The Debate on the European Union’s Future From the Perspective of Regional Members of Parliament

Differentiated integration has become ubiquitous in the European Union today. However, the evaluation of differentiated integration by the academic community is much contested: While some see it as a remedy to political gridlock, others think of it as the beginning of the end of the EU (i.e., disintegration). Our article sheds light on the relationship between differentiated integration and disintegration from the viewpoint of subnational members of Parliament. Assuming that at least some scenarios of differentiated integration are related to disintegration, we report on data from a survey of seven EU member states about subnational members of Parliament’s preferences regarding future scenarios for the EU. Our res‐ ults find that a preference for a Europe with a singular focus on “nothing but the single market” is related to a functionalist approach towards European integration and the perceived disintegration of the EU. This preference is especially preval‐ ent among subnational MPs in the Czech Republic and Poland, both known for having opt‐out solutions. While the Czech Republic constantly shows high levels of Euroscepticism in public surveys, the reverse is true in Poland. Obviously, a gen‐ eral commitment to the EU should not be equated with a shared common goal of further European integration. If such differences become permanent, European integration may genuinely be endangered.


Introduction
Since the major rounds of enlargement of the European Union in the 2000s and early 2010s, increasing heterogeneity among member states can be observed and, consequently, the rise of differentiated integration (Leuffen, Rittberger, & Schimmelfennig, 2022). The concept of differentiated integration has been used to refer to the diverse modes of integration within the EU (Gänzle et al., 2020). However, the question arises as to how many differences and how much differentiated integration a community or political project can bear (Hooghe & Marks, 2022). For some authors, differentiated integ-ration is perceived as a "double-edged sword" (Chopin & Lequesne, 2016) or as "poison or a panacea" (Lord, 2015) because differentiation can function as a driver for deepening EU integration as well as its disintegration. Our article aims to investigate the relationship between differentiated integration and disintegration. The EU future scenarios (European Commission, 2017) are considered indicators of certain preferences for differentiated (dis)integration (Leruth et al., 2019b). Until now, these scenarios have been rarely used in studies (Goldberg et al., 2021;Praprotnik & Perlot, 2021).
Differentiated integration concerns not only the national level but also the sub-national level (Dyson & Sepos, 2010). In this contribution, we use data from a novel survey among regional (subnational) members of Parliament (MPs) from seven EU member states to analyse scenarios of differentiated (dis)integration. The subnational level can be affected by "multi-level differentiation" (Fumasoli et al., 2015), which describes the influence of differentiation on various levels in the EU. In many EU member states, the sub-national level is responsible for the legal implementation of EU law in various policy fields (Borghetto & Franchino, 2010). Regions still have limited influence in the EU multi-level system. In the course of deepening EU integration, regions have faced a loss of competence in the EU. In return, they demanded enhanced rights in shaping EU policy at both the domestic and EU levels (Abels & Battke, 2019;Panara, 2015). In this context, regional parliaments can make use of different extra-state and intrastate channels (Bauer & Börzel, 2011). The Lisbon Treaty introduced a central measure for empowering (regional) parliaments in 2009. Regional parliaments have been given the opportunity to participate in the early warning system (EWS) for subsidiarity control (Bursens & Högenauer, 2017). Theoretically, the EWS can be used by regional parliaments to set claims for differentiation directly. However, participation in the EWS is only possible for regional parliaments with legislative competencies and depends on national parliaments' assessment of whether regional parliaments should be consulted in this process (Högenauer, 2019). Tight time frames and limited resources on the side of the regional parliaments make the EWS a rather exclusive way of participation. Beyond limited formal rights (domestic involvement in EU affairs, Committee of the Regions, EWS), regional MPs must rely on informal contacts and networks (Schneider et al., 2014) to push their agenda. Apart from regional parliaments' involvement in EU policy-making, the regional level can be a breeding ground for discontent and support for European disintegration. Dijkstra et al. (2020) found regional disparities to be a main driver for anti-EU voting. This result also mitigates the objection that regional elections are often considered second-order elections. Schakel and Jeffery (2013) criticise the applicability of the secondorder election model with regard to regional elections and found out that regional elections are not second-order elections per se. A more nuanced perspective on regional elections is called for, as studies on regional elections acknowledge (Bolgherini et al., 2021;Gougou, 2023;Liñeira, 2016;Linek & Škvrňák, 2022). Moreover, regional-level coalition-building may serve as an opportunity to test the fit of two or more coalition partners before implementing any such coalition at the national level. Coalition building among Eurosceptic forces at the regional level should thus be observed from an early stage. Additionally, the regional level is often deemed "closer to citizens" (Piattoni, 2010), which makes the investigation of regional politicians' attitudes towards European integration particularly rel-evant. To some extent, at least, regional MPs "mirror" the attitudes of their constituencies since they are elected representatives. Conversely, (regional) politicians can also act as top-down opinion leaders in their constituencies regarding preference formation on the EU's future development (Telle, de Blok, et al., 2022a).
Studies by Leuffen, Schuessler, and Gómez Diáz (2022), Schuessler et al. (2022), and Telle, Badulescu, et al. (2022) found that differentiated integration can be linked to disintegration under certain conditions despite its perception as being a political instrument for dealing with heterogenous preferences (Adler-Nissen, 2011). Building on these contributions, our article aims to investigate the potential consequences of EU future scenarios and the relationship between differentiated integration and disintegration more closely from the viewpoint of regional MPs. Our research questions are as follows: • Are differentiated integration and disintegration linked to each other from the viewpoint of regional MPs, and if so, how? • Which scenarios for differentiated integration are associated with pro-European attitudes, and which can be associated with attitudes opposing further European integration?
Moreover, we concentrate on the Single Market Only scenario, which represents the notion of "à la carte Europe" (Stubb, 1996) because this scenario may trigger disintegrative developments as recent scholarship indicates Telle, de Blok, et al., 2022). Following this, our further research questions address the following aspects: • How prevalent are preferences for this scenario (Single Market Only) among regional MPs? • Which political strategies in EU affairs are linked to this scenario at the regional level?
Our results find that at least some scenarios for a future Europe are linked to disintegration from regional MPs' viewpoint. The analysis shows that a preference for future scenarios focusing on economic integration and "doing less more efficiently" is associated with anti-European attitudes and a high perceived likelihood of EU disintegration. The structure of this article is as follows: Section 2 provides an overview of both concepts, differentiated integration and disintegration, argues for possible linkages, and embeds our research questions within a literature review. Next, Section 3 introduces the methods and data used in our analysis. In Section 4, using a novel survey among regional MPs in several EU member states, we then explore the relationship between differentiated integration and disintegration empirically. Finally, in Section 5, we discuss our results and implications for future research.

Differentiated Integration: A Remedy or Harmful to European Integration?
While processes of differentiation are an essential part of a politically and socio-economically heterogeneous EU (Gänzle et al., 2020), differentiated integration is, nevertheless, contested. The European Commission (2017), which describes various future scenarios in their White Paper on the Future of Europe: Reflections and Scenarios for the EU27 by 2025, notes that differentiation can either be seen as part of the problem or part of the solution. This contested perspective on differentiation can also be found in scholarship on differentiated (dis)integration. On the one hand, differentiated integration is perceived as a policy-making tool to avoid political deadlock and accommodate the heterogeneity of political preferences at the supranational EU level and among member states. From this perspective, differentiated integration can deepen the EU integration process (Adler-Nissen, 2011;Dyson & Sepos, 2010;Kölliker, 2001;Schmidt, 2019). On the other hand, increasing differentiation can also promote disintegrative developments, as Kelemen (2021, p. 679) suggests: "If taken to an extreme, DI [differentiated integration] could contribute to European disintegration through a process of fragmentation and atrophy." For a comprehensive understanding of differentiation which includes perspectives on both integration and disintegration, we have followed Leruth et al. (2022), who suggest using the term differentiation as an "umbrella term referring to heterogeneous modes of integration and disintegration in the EU" (Leruth et al., 2022, p. 10). Differentiated integration is multifaceted and only certain aspects of it have the potential to fuel disintegration. Schimmelfennig andWinzen (2020a, 2020b) follow Stubb's (1996) seminal typology by relabeling its categories as "multi-speed" (time), "multi-tier" (space), and "multi-menu" (matter) differentiation. Schimmelfennig et al. (2022) emphasise the importance of duration when distinguishing between temporary and permanent states of differentiated integration. One can easily imagine that these various forms of differentiation have different consequences regarding deepening or loosening European integration. While permanent differentiation might lead to irreversible manifestations of differentiation (perhaps even disintegration), temporary agreements can be taken back if they become useless, obsolete, or unnecessary. While in a "multi-speed" Europe, differentiation might lead to uniformity in a reasonable timeframe, a "multi-menu" Europe implies no convergence towards uniformity (Schimmelfennig et al., 2022, p. 4). The current main drivers of differentiation are an instrumental-or capacity-driven logic and a constitutional-or sovereignty-driven logic, according to Schimmelfennig et al. (2022). Instrumental-or capacity-driven differentiation refers to concerns about distribution and efficiency in the context of EU enlargement (Schimmelfennig et al., 2022, p. 5): For "old" mem-ber states, these tend to be concerns about redistribution of funds and cost distribution, which arise in the process of enlargement; for "new" member states, these tend to be concerns about market and regulatory processes on domestic products. By contrast, constitutional differentiation captures the heterogeneity of preferences regarding a deepening of European integration among member states . While instrumental-or capacity-driven differentiation is typical in a multi-speed Europe, constitutional differentiation is likely to become durable and relates to multi-menu differentiation (Schimmelfennig et al., 2022, p. 5). Constitutional differentiation refers to the concerns of member states and governments about shifting competencies to the supranational EU level and relates them to the idea of protection of national sovereignty and identities. These motives are currently dominant in member states with strong (exclusive) national identities. Concerns about sovereignty and increasing national pride provide a fruitful ground for a constitutional-driven logic, as we can currently observe in some Central and Eastern Europe (CEE) countries. De Blok and de Vries (2022) and Leuffen, Schuessler, and Gómez Diáz (2022) find that Eurosceptic citizens more commonly support opt-outs, whereas pro-European citizens tend to be more indifferent towards differentiated integration. Pro-European citizens are more supportive of a multi-speed Europe to overcome political deadlocks, while Eurosceptic citizens are most supportive of opt-outs, mainly driven by national sovereignty concerns. As previously pointed out, permanent differentiation, especially a "multi-menu" Europe scenario and a constitutional-or sovereignty-driven logic, can evoke disintegrative developments. This allows a connection to research in EU disintegration.
In contrast to the scholarship on differentiated integration, the scholarship on EU disintegration is comparably young and has only in the last decade attracted increasing attention, mainly due to Brexit (Eppler et al., 2016;Grimmel, 2020;Leruth et al., 2022;Vollaard, 2014Vollaard, , 2018Webber, 2019). As discussed below, member states' sovereignty-based concerns are important in understanding EU disintegration. Webber (2019) conceptualises disintegration as a three-dimensional construct. Sectoral disintegration refers to a reduction in the number of policy fields in which the EU exercises exclusive or shared competencies. Vertical disintegration is the reduction of treaty-based responsibilities. Horizontal disintegration means a decline in EU members. In this understanding, disintegration is a possible consequence of the renationalisation of EU competencies. Moreover, Vollaard (2014Vollaard ( , 2018) provides a complex framework for polity formation and conceptualises two dimensions of disintegration, an actor-level and a systemic level. He defines dis(integration) as follows: "Integration concerns the making of a system of authoritative allocations from other systems of authoritative allocations, whereas disintegration is the unmaking of such a system" (Vollaard, 2018, p. 5). Missing options for "full exit" and "effective voice" can lead to disintegrative developments since member states seek to call for more opt-outs and the renationalisation of competencies. Against this background, Vollaard (2018, p. 7) assumes: "The EU will thus be limping ahead with many rather grudgingly accepting it as the least unattractive option." Since regional actors lack opportunities to raise their "voice" in the EU's multi-level system efficiently, they can be a specific source of discontent in the current system. EU disintegration can have different manifestations and should be perceived as a process. This evaluation is also shared by Leruth et al. (2019aLeruth et al. ( , p. 1391, who agree that a full rupture involving cutting all ties without making provisions on handling future relations by (legal) agreements would be nearly impossible due to global interdependencies. Schimmelfennig (2018Schimmelfennig ( , p. 1154) describes this process using the term "differentiated disintegration," which implies a "selective reduction of a state's level and scope of integration." Leruth et al. (2019bLeruth et al. ( , p. 1015) point to the multidimensionality of such differentiated disintegration: "as the general mode of strategies and processes under which (a) member state(s) withdraw(s) from participation in the process of European integration (horizontal disintegration) or under which EU policies are transferred back to member states (vertical disintegration)." Here, in addition to the re-transfer of competencies from supranational to the member-state level, aspects of reduced cooperation between political actors and EU actors in shaping EU policy are also included. Moreover, Leruth et al. (2019bLeruth et al. ( , pp. 1023Leruth et al. ( -1025) make a case for there being three major scenarios of European (dis)integration which theoretically acknowledge the spectrum of possibilities: (a) "breaking down," in which the EU fails completely due to a lack of willingness or ability of EU member states to deal collectively with challenges; (b) "muddling through," which describes the reliance on existing institutional structures to maintain the status quo; (c) "heading forward," in which crises such as Brexit may elicit a deepening of cooperation. At least some forms of differentiated integration, that is to say, those centring around an increase of national sovereignty while at the same time lowering commitment towards European integration, are important in this respect.
To summarise, the following can be concluded from the brief review of the relationship between differentiated integration and disintegration. Three characteristics of differentiated integration seem to be crucial in this relationship. First, a temporal dimension distinguishes between permanent and temporary differentiated integration; second, the existence of a common goal regarding European integration versus fears about protecting member states' sovereignty; and third, the processuality of differentiated (dis)integration. Based on our research questions, we expect that differentiated integration and disintegration are linked to each other and that certain EU future scenarios are associated with pro-and contra-Europeanness. The following hypotheses structure our data analysis: • H1: Regional MPs' preferences for scenarios involving less cooperation are linked to the perception that the EU might face disintegration in the future. • H2: Regional MPs preferring scenarios such as "Single Market Only" and "Doing Less More Efficiently" state more often that European integration has already gone too far. • H3: Preferences for a Single Market Only scenario (multi-menu differentiation) are more likely in CEE countries due to sovereignty-based concerns. • H4: Preferences for a Single Market Only scenario are not only related to lower support for further European integration (H2) but also to preferences for more competition and less cooperation at the regional level in the EU.
Since the future scenarios used in this article are indicators for political (dis)integration, we are only able to concentrate on the political dimension of EU (dis)integration (Eppler et al., 2016). As the review on differentiated (dis)integration has shown, differentiated integration, despite its usefulness as an instrument for deepening integration (Adler-Nissen, 2011; Schmidt, 2019), can evoke disintegrative developments if certain conditions apply. Certain forms of differentiated integration, such as the "multi-menu" Europe, have the potential to fuel disintegrative processes, as Schuessler et al. (2022) and Telle, Badulescu, et al. (2022) discuss. Sovereignty-based concerns, in particular, have been found to be drivers of EU disintegration.

Methods and Data
Empirical research on differentiated integration and disintegration has, until now, mainly focused on two scenarios: "multi-speed Europe" and, referring to multiple preferences for opt-outs, "multi-end Europe" Moland, 2022;Telle, Badulescu, et al., 2022;Telle, de Blok, et al., 2022). Nevertheless, Börzel (2018), Leruth et al. (2019b), and Schuessler et al. (2022) criticise the use of such a simplified scale and strongly argue for the use of more sophisticated approaches to measuring European (dis)integration. These authors argue that measurements should refer to the full continuum of European (dis)integration, from "heading forward" to "breaking down" (Leruth et al., 2019b). Applying such kinds of measurement, we argue, is not only a more valid measure of theoretical assumptions but also necessary in presenting symmetric item batteries, including positive, neutral and negative scenarios to survey respondents. To this end, we included two item batteries in our questionnaire, the first focusing on various states of differentiated integration and the second which also addresses scenarios of disintegration.
The first item battery includes future scenarios about the EU, as introduced by Jean-Claude Juncker in the White Paper on the Future of Europe: Reflections and Scenarios for the EU27 by 2025 (European Commission, 2017). The White Paper presents five different scenarios about the future development of the EU, ranging from Carrying On (i.e., the status quo) to scenarios in which there is less integration ("Nothing but Single Market" and "Doing Less More Efficiently") to scenarios of (differentiated) integration ("Those Who Want More Do More" and "Doing Much More Together"). Although these scenarios do not directly refer to the term differentiated integration, Leruth et al. (2019bLeruth et al. ( , p. 1014) find them to be valid measures for differentiated (dis)integration, since the concept is at least implicitly inherent in the scenarios, particularly Scenario Three (Those Who Want More Do More): "However, while the document avoids referring to the term of differentiated integration expressis verbis, the concept is implicitly present in the third scenario" (Leruth et al., 2019b(Leruth et al., , p. 1014. Furthermore, Leruth et al. (2019b) argue that Scenario Two (Nothing but Single Market), as well as Scenario Four (Doing Less More Efficiently), can be understood in terms of differentiated disintegration. Considering the political relevance and the spectrum addressed by the future scenarios in the White Paper, it is surprising that they have rarely been used in empirical studies until now (Goldberg et al., 2021;Praprotnik & Perlot, 2021). Our survey respondents were asked to state whether these future scenarios are good or bad options on a scale from 1 (very good option) to 4 (very bad option).
We addressed disintegration even more concretely in our second item battery, where we followed Leruth et al. (2019bLeruth et al. ( , pp. 1023Leruth et al. ( -1025 in considering "breaking down," "muddling through," and "heading forward" as possible scenarios. Thus, four major scenarios were included in the second item battery in which: (a) the EU Fails Completely, (b) More Countries Leave the EU, (c) Cooperation Continues as Before, and (d) Cooperation Between Member States Deepens. Respondents were asked to rate the likelihood of these options on a fourpoint scale (1 = very likely, 4 = very unlikely). Once again, we aimed to offer a symmetric item battery including a continuum of possible scenarios from the dissolution of the EU to a deepening of integration. Section 4.2 examines the relationship between our two item batteries (future scenarios and item battery on disintegration) more closely.
Our data was collected by an online survey undertaken between autumn 2020 and winter 2021. The survey was part of the REGIOPARL project, which aimed to investigate the activities of regional parliaments in EU affairs and the perception of European integration from the viewpoint of regional deputies. Our research was conducted in seven member states: Austria, Germany, Italy, Spain, France, the Czech Republic, and Poland. This country selection was guided by considerations of geographical scope and with a view to representing "old" and "new" member states, federal and centralised political systems, and "strong" and "weak" regional parliaments with respect to their competencies (cf. Table 1). We used the Regional Authority Index (RAI; Hooghe et al., 2016;Schakel, 2023) to take regional "power" in the domestic context into account. The RAI measures the authority in self-rule and shared rule exercised by regional governments on 10 indicators and ranges from 0 to 30. When comparing the selected countries, it becomes obvious that three can be described as centralised states whose regional parliaments have no legislative power, as reflected by their comparatively low RAI values. Especially in Poland and the Czech Republic, regional authorities only exert weak power over their national counterparts. We are going to take these differences into account when interpreting our empirical findings later on.
Our standardised questionnaire included 28 questions about regional MPs' general attitudes to European integration, their professional activities, and political strategies, and questions on their networks in the EU's multi-level system. The survey was conducted using the program Lime Survey. We translated questionnaires into the respective languages of each country and used a multi-step procedure for contacting regional MPs (by email, post, and telephone). Additionally, we asked regional parliaments' head offices to support our research and sought multiplicators, such as universities, in the respective countries. We have contacted all regional parliaments and their deputies in the respective countries. We yielded satisfying though varying response rates for the total sample compared to similar studies targeting (regional) deputies as a group of interest ( Table 2). The total average response rate of our survey across all countries was 29.8%, in line with similar surveys of Wonka (2017), who conducted a survey in the German Bundestag, yielding a response rate of 16%, and Schneider et al. (2014), who report on a survey among German regional MPs that had a response rate of 28.5%. Nevertheless, despite the same procedure for conducting fieldwork being used uniformly, country samples vary. While we were able to reach a representative spectrum of political parties in Germany and Austria, respondents in France and Italy were less likely to participate in the survey. Response rates in regions of the two CEE countries, the Czech Republic and Poland were quite satisfactory. The PiS party is clearly underrepresented in the Polish sample, although not completely absent. We can report no major deviations concerning gender compared to actual distributions in the regional parliaments at the time of the survey. We can also report a fairly even participation rate across individual regions for each country surveyed. Our sample can be described as fairly pro-European for all countries since Eurosceptic MPs and parties were harder to reach than their pro-European counterparts. These limitations should be kept in mind by readers when turning to our results in the next sections. Regional MPs are, like all politicians, a hard-to-reach population and have not been surveyed that often. This makes our data set innovative, and our results give a relevant first insight into their attitude patterns on European (dis)integration.

Empirical Analyses and Findings
Our analysis investigates our theoretical assumptions as follows: First, we present univariate distributions of general attitudes towards European integration and the perceived advantages for each region of being in the EU from the viewpoint of regional MPs; second, we examine bivariate correlations of scenarios of differentiated integration and disintegration; third, we examine the relationship of these scenarios with perceived advantages for each region being in the EU; fourth, we conduct a multiple linear regression analysis to investigate which scenarios are linked to attitudes that are pro-European integration and which are linked to the perception that European integration has already gone too far. In the fifth and final step, we focus on one scenario, multi-menu differentiation (i.e., the Single Market Only scenario) and ask for its prevalence and its association with political strategies at the regional level. The exact wording of the survey questions can be found in the Supplementary File.

European Integration, Differentiated Integration, and Disintegration From the Viewpoint of Regional Members of Parliament
We asked regional MPs to rate the level of European integration by asking a question commonly used in large-scale surveys: Some say that European integration should be pushed further. Others say it has already gone too far. What is your opinion regarding this topic? Zero means that European integration has already gone too far, and 10 means that European integration should be pushed further. Five is equivalent to the opinion that European integration has reached a satisfactory level. Figure 1 shows boxplots of the answers to this question, revealing Spanish regional MPs to be very much in favour of European integration, while Czech and French regional MPs are comparatively sceptical about further integration. The mean values of the Czech and French regional MPs are somewhat low, while we find an upper quartile of German, Spanish, and Italian regional MPs who state that European integration should be pushed even further. We analysed country differences also regarding party profiles. In all countries except France members of right-wing parties in our sample agree that European integration has already gone too far. As already stated in the description of our sample, members of Eurosceptic  parties were hard to reach in all participating countries, which makes our sample in all countries more pro-European. Additionally, MPs have been sceptic about providing personal information in our survey due to concerns about anonymity, which leads to a considerable decrease in sample sizes on these questions.
As well as asking regional MPs about their attitudes towards European integration, we were interested in opinions on the perceived advantages and disadvantages of a region in the EU. Being in the EU is rated as an advantage by the majority of regional MPs in all participating countries surveyed (Table 3). Regional MPs in Poland especially rate their country's membership in the EU very positively (47.4% of Polish MPs surveyed are convinced that being in the EU is advantageous to the region). Once again, by contrast, French and Czech regional MPs are less enthusiastic about being in the EU. Taking the eta-squared value as a measure of association between nominal and interval data suggests a slightly significant and positive association between country and perceived advantages for the region being in the EU (eta 2 = 0.246; p = 0.001).
In the next step of our analysis, we ask how scenarios of differentiated integration and disintegration are related to each other and which are related to perceived advantages for a region of being in the EU (Table 4). We find that all scenarios with less integration or disintegration are related to each other and negatively correlate with scenarios representing the status quo or a deepening of integration. Thus, Nothing but Single Market, Doing Less More Efficiently, Doing Much More Together (negative correlation), EU Fails Completely and Is Dissolved, and Advantages for a Region of Being in the EU build one cluster of attitudes, which can be described as an instrumental approach towards European integration. Perceived advantages for the region of being in the EU seem to be influenced by economic concerns and a rejection of further and deeper integration. We will analyse this instrumental approach towards European integration and its relationship with the political strategies of regions in more detail in the last part of our results section.

Scenarios Representing Differentiated (Dis)Integration: Pro or Contra European Integration?
In this section, we aim to show how different scenarios of differentiated (dis)integration relate to attitudes toward European integration in general. To this end, we use our general question on European integration, with answers ranging from 0 to 10, as a dependent variable for multiple linear regression analysis. Various scenarios on differentiated (dis)integration serve as independent variables. We excluded scenarios that have either proven to be highly correlated or address similar aspects of European integration (cf. Section 4.1). All independent variables have been dichotomised to ease interpretation and to provide a parsimonious model. Four scenarios are   clearly negatively linked to European integration, namely Nothing but Single Market, Doing Less More Efficiently, EU Fails Completely and Is Dissolved, and More Countries Leave the EU (Table 5). Therefore, we can conclude that a preference for these scenarios not only reflects aspects of differentiated (dis)integration but is explicitly associated with the perception of disintegration. Four scenarios representing the status quo or a deepening of integration are positively linked to a general attitude toward European integration, although the coefficients are comparatively small. Our analysis yields a satisfactory adjusted R² value of 0.433 which can be mainly attributed to the explanatory power of the four variables addressing differentiated disintegration.

Preferences for Multi-Menu Differentiation, Preferred Regional Strategies in European Union Affairs, and Prevalence of Scenarios Across Countries
A prominent scenario on differentiated European integration is the Single Market Only scenario which aims to shift competencies towards the member states and constrain EU action to the single market only. This scenario indicates a preference for economic integration and represents multi-menu differentiation or a "Europe à la carte." In the last section of our data analysis, we turn from a more general analysis of attitude patterns in the broad context of European integration back to a more detailed regional perspective. We aim to investigate which political strategies at the regional level can be associated with a preference for the Single Market Only scenario. To this end, we use two metric indices as independent variables measuring a preference for either "regional competition" or "transregional cooperation" in EU affairs. These indices have been developed using exploratory factor analysis (cf. Donat & Lenhart, 2023) applied to an item battery on regional strategies in EU affairs in our survey. We asked regional MPs which strategies and goals they pursue in EU affairs for their region. The "regional competition" strategy includes two items: (a) "Achieve as many advantages as possible for my region" and (b) "raise as many funds as possible for my region." The "regional cooperation" strategy includes three items: (a) "Make EU's achievements more visible in my region," (b) "deepen cooperation with other European regions," and (c) "pay greater attention to the European perspective in my decision-making." Both indices range from 1 (strongly agree) to 5 (strongly disagree). We dichotomised answer choices of our dependent variable "preference for the single market scenario only" and computed a binary logistic regression. Model 1 (M1, Table 6) illustrates that. Regional MPs who prefer the "regional competition" strategy are more likeable to prefer a Single Market Only scenario for European integration. The model fit improves considerably when adding country dummies to our model (M2, Table 6). The results of M2 indicate a strong preference for the Single Market Only scenario in Poland and the Czech Republic. Regional MPs in Poland have a 4.216 higher probability and regional MPs in the Czech Republic have a 5.417 higher probability of preferring this scenario than the reference group of regional MPs in Germany. Regional MPs in France and Austria also show a higher probability of preferring this scenario than the reference group but comparatively lower than their colleagues in Eastern Europe. The effect for regional MPs in Italy is only significant at p = 0.05 and should be treated with caution due to the small sample size in Italy. We also find significant effects for the two indices, although the "regional cooperation" effect is again very low. Regional Notes: Unstandardised coefficients (B), standard error (SE), and measures of fit from multiple linear regression; dependent metric variable from 0 (European integration has already gone too far) to 10 (European integration should be pushed further); *** p < 0.001, ** p < 0.01, * p < 0.05. Notes: Odds ratio (OR), standard error (SE), and measures of fit from logistic regression; dependent variable of 1 (very likely or somewhat likely) or 0 (very unlikely or somewhat unlikely); *** p < 0.001, ** p < 0.01, * p < 0.05.
MPs favouring a regional competition strategy have a 1.748 higher probability of preferring a Single Market Only scenario compared to MPs who do not. In sum, our analysis indicates some country-specific differences. While regional MPs from Poland rate European integration and the advantages for its regions from being in the EU quite positively, they clearly tend to prefer economic integration. This is even more true for regional MPs from the Czech Republic, who are comparatively sceptical about European integration and the perceived advantages for the region, having the strongest preference for the Single Market Only scenario. Turning to our hypotheses in Section 1, we find evidence for H1, H2, and H4. In H3, we assumed a preference for the Single Market Only scenario, especially in our CEE countries, Poland and the Czech Republic. Additionally, our comparison also indicates a remarkable preference for this scenario in France, which leads us to discuss possible explanations for this effect in the final section of our article.

Discussion and Conclusion
Our analysis aimed to elaborate on the relationship between differentiated integration and disintegration from the viewpoint of regional MPs. We offered our respondents scenarios representing differentiated integration and disintegration, providing a symmetric measurement of these two phenomena. Concerning our main research question on the relationship between differentiated integration and disintegration, we find at least certain scenarios associated with disintegration under certain circumstances. The Single Market Only scenario explicitly assumes a reversion of competencies from the EU to the national level; a preference for this scenario can serve to breed ideas which assume disintegration. "Pick and choose" or opt-outs lead to the avoidance of uncomfortable policies in the European Community . It is especially this "Europe à la carte" which leads De Blok and de Vries (2022) to doubt whether differentiated integration will decrease heterogeneity within the EU. Additionally, Telle, de Blok, et al. (2022) assess that this scenario bears the potential for permanent differentiated integration. While temporary differentiated integration can help overcome gridlock, permanent differentiated integration can lead to irreversible forms of disintegration. Whether disintegration becomes dangerous for a political system's stability depends on the system's ability to balance integrative and disintegrative elements. Vollaard (2018) argues that integrative and disintegrative elements, or centripetal and centrifugal powers, can exist in political systems at the same time. The more political communities grow, the more interests they have to integrate. This "natural" differentiation leads to different competencies and responsibilities among the single units, as observed in many asymmetric federal systems, which is also the case in some of our sampled countries. Political systems can handle this divergence if subunits are loyal while also having the opportunity to voice their concerns (Vollaard, 2018).
Additionally, we find evidence that a Single Market Only scenario, which is associated with strategies of competition at the regional level, is much more likely to be preferred in Poland and the Czech Republic. Cianciara (2022, p. 538) describes Poland as the "champion of internal differentiation in post-Brexit Europe." Although very pro-European in public opinion surveys, Poland currently refuses to go beyond traditional areas of integration such as the single market. Its alternative vision of a "Europe of nation-states" is clearly undermining further European integration (Gagatek et al., 2022, p. 13). Similar assessments can be found for the Czech Republic, which, together with Sweden, joined even more differentiation projects than Poland before 2018 (Cianciara, 2022, p. 540). Contrary to Poland, public surveys show a consistently high rate of Euroscepticism among the Czechs (Smekal & Havlík, 2022). Havlík and Havlík (2018) have analysed the great interest of the Czech Republic in accessing funds. Returning to our research question, we find preferences for multi-menu differentiation, especially where the ideological environment is already conducive to disintegration. Additionally, differing goals for European integration might also be grounded in the fact that regional actors in Poland, the Czech Republic, and France lack a "voice." Vollaard (2018) assumes that limited opportunities to have a "voice" in the EU lead to opt-outs. Regional actors in these three countries are embedded in centralised systems and have no legislative powers (cf. Table 1). These characteristics might also be responsible for a functionalist or instrumental approach towards European Integration, with a focus on economic instead of political integration. Further research should investigate the origin of this attitude pattern (preference for the single-market scenario) more indepth, comparing regional and national attitudes. If this pattern is caused by limited opportunities for regions to raise their "voices," we should find different patterns at the national level, which is much more powerful in the EU's multilevel system. If such attitudes are grounded in ideological roots, they might also prevail at the national level. The "skewness" of our sample regarding its "pro-Europeaness'' limits the possibility for investigating these aspects more closely. Additionally, including Nordic countries in our analysis could increase our sample's empirical basis for centralised states.
Our analysis focused on a specific dimension of European Integration: political integration. Spillover effects towards other dimensions, such as social, cultural or economic integration, do not necessarily occur but are at least to some extent influenced by the framework political actors and systems provide (Eppler et al., 2016). Our research follows the design of a cross-sectoral analysis and provides some initial insight into the relationship between differentiation and disintegration. Crises can exert a major influence on the process of integration and disintegration (Vollaard, 2018). Currently, we perceive a great fear of history repeating itself in many CEE countries, given the Russian invasion of Ukraine. It seems that, at least in some respects, countries such as Poland have widened their interest in European integration bey-ond merely economic aspects. Yet we cannot anticipate how long this attitude change will endure or how deep it will be. Leruth et al. (2019b) emphasise the potential of crises to lead to windows of opportunity for more integration. Given the currently volatile political situation in the EU and beyond, we agree with Börzel (2018) in arguing strongly for longitudinal studies on disintegration to better understand its causes and consequences.
Our findings empirically illustrate the complex relationship between differentiation and disintegration and its association with political strategies at the regional level. Formal ways of engaging in EU affairs, such as participation in the EWS, are limited for regional MPs, as described at the beginning of our article. Hence informal ways such as networking or lobbying are an important resource for receiving and spreading information or attempting to set claims in the EU. Whichever path regional MPs choose, attitudes-for example, about the EU's future-are an important pre-determinant of their EU engagement. On the other hand, it becomes clear that a lack of say leads to ignorance and withdrawal in the long run. Our research contributes to the rare empirical studies in this field, which until now have mainly focused on population surveys. Complementary surveys among politicians can widen our understanding of preferences and perceptions in the context of European integration, in which the regional level is one player among many.

About the Authors
Elisabeth Donat is head of the department at the Department of European Policy and the Study of Democracy at the University for Continuing Education Krems. She has previously worked at the Department of Sociology at the Universities of Vienna, Innsbruck, and Salzburg. Elisabeth Donat finished her study in sociology at the University of Vienna. In her research projects, she prefers inter-and transdisciplinary work and is interested in the role of regions (subnational units) in the EU's multi-level system.
Simon Lenhart is a research associate at the Institute of Political Science, FernUniversität in Hagen. Previously, he worked at the Department of European Policy and the Study of Democracy at the University for Continuing Education Krems. Simon's research focuses on EU integration, especially the involvement of the subnational level in EU affairs and policy analysis.