Can Accommodation Work? Electoral Eﬀects of Mainstream Left Position-Taking on Immigration

Frederik Hjorth∗ Martin Vinæs Larsen†

This version: September 27, 2019

Abstract

In many countries, right-wing populist parties have gained electoral support by attracting

voters from mainstream left parties. This has prompted public and scholarly debate

about whether mainstream left parties can regain political power by taking a more

restrictive position on immigration, a so-called ‘accommodation’ strategy. However,

selection bias confounds observational estimates of the eﬀectiveness of this strategy.

We implement a survey experiment during a unique political situation in Denmark

where the mainstream left party’s position on immigration is ambiguous, allowing us to

manipulate voters’ perceptions of its position. We show that consistent with spatial

models of politics, accommodation attracts the most anti-immigration voters and repels

pro-immigration voters. Because repelled voters defect to other left parties, while

attracted voters come from right parties, accommodation increases overall support for

parties supporting a mainstream left government. The results demonstrate that in some

contexts, accommodation can improve the political prospects of the mainstream left.

Keywords: party politics, issue voting, immigration, spatial models

∗Assistant Professor, Department of Political Science, University of Copenhagen. †Assistant Professor, Department of Political Science, Aarhus University. The Social Democratic party family ranks among the most successful political projects in modern European political history. In the two decades following World War II, vote shares for Social Democratic parties exceeded 30 percent across all European democracies (Benedetto et al., 2019). However, starting in the 1980’s, right-wing populist parties successfully peeled significant numbers of voters off the Social Democratic coalition, in no small part by appealing to anti-immigration sentiments of traditionally left-wing voters (Givens, 2005). This places contemporary Social Democratic and similar mainstream left parties in a strategic dilemma (Bale et al., 2010). As right-wing populist parties continue to attract anti- immigration voters, mainstream left parties can either respond by taking a more restrictive position on immigration, or move to the left in order to appeal to new groups of voters. Meguid (2005), building on a spatial model of party and voter behavior, labels these strategies respectively “accommodative” and “adversarial”, a terminology we adopt here. While Meguid’s conceptual framework has been highly influential, empirical scholarship on the electoral effects of these competing strategies remains inconclusive. Existing observational work finds negative (Dahlströmand Sundell, 2012) as well as positive (Spanje, 2018) associations between mainstream party accommodation and right-wing populist support. In this article, we challenge prevailing approaches to studying the electoral effects of mainstream left responses to right-wing populist parties. We argue that existing approaches have an overly narrow focus on electoral support for the mainstream left party in contexts where the party’s political success depends on all parties supporting a mainstream left government, and that existing approaches do not effectively address problems related to credibly identifying the effect of accommodative strategies. Building on this argument, we design and implement an experiment in a nationally representative sample of voters. We exploit a rare situation in which government negotiations create credible ambiguity about the position of Denmark’s Social Democrats on immigration, allowing us to effectively manipulate respondents’ perceptions of their position. Contrary to some earlier findings, our results indicate that a strategy of accommodation from the Social Democratic party can raise

1 electoral support for the left as a whole. Subgroup analyses show that, consistent with the spatial theoretical framework, the effect is driven by electoral gains for the Social Democrats among anti-immigration voters who usually vote for right-wing parties. While we find that accommodation on the issue of immigration can improve the political prospects of the mainstream left, this does not imply that it is the only way to do so. For example, recent work suggests mainstream left parties can successfully appeal to socio-cultural professionals (Abou-Chadi and Wagner, 2019). The effectiveness of accommodation also plausibly depends on the institutional context, a question we revisit in the concluding section. Beyond giving us an insight into the how the mainstream left may deal with the challenge from right-wing populist, our study provides an important corrective to research suggesting that parties are increasingly ‘weak’ actors. In spite of the power of partisanship at the individual level (Barber and Pope, 2019) and issue ownership at the party level (Seeberg, 2017), parties can still affect their electoral fate through strategic positioning on salient issues.

Challenges in Studying Electoral Effects of Party Strategy We highlight two problematic practices in the existing literature, one theoretical and one methodological. At the theoretical level, we challenge the existing literature’s singular conceptualization of mainstream left party success in terms of electoral support. As originally argued by Strøm (1990), parties may pursue office-seeking as well as vote-seeking strategies, and the former may come at the expense of the latter. Specifically, in a spatial model, a mainstream left party may see little or no vote gain from moving to the right on immigration, because vote gains from anti-immigration voters is offset by losses among pro-immigration voters. But because this latter group of voters will tend to defect to other parties on the left, accommodation is likely to increase the mainstream left party’s chances of forming a government based on a coalition of other left parties. (In Appendix A, we show that mainstream left parties often find them self in such a strategic position). Due to this plurality of motives, electoral support for the mainstream party itself is not the only relevant dependent variable when evaluating the effects of party strategy in a multiparty system.

2 At the methodological level, we highlight the risk of endogeneity in observational studies of the effects of party position-taking on electoral support. This risk arises from the fact that the ‘treatment’ – i.e., mainstream left party position – is in all likelihood not independent of parties’ potential outcomes with respect to electoral support. For example, studying a cross-section of Swedish municipalities, Dahlströmand Sundell (2012) find that “tougher” mainstream left party positions on immigration are associated with higher support for the Sweden Democrats. Similarly, in a cross-country sample, Krause et al. (2019) update and extend Meguid (2005), finding no association between mainstream left party positions on immigration and right- wing populist party support. The inherent challenge in these observational studies is that mainstream left positions may be endogenous to expected changes in right-wing populist party support. Specifically, if national or local parties who believe they stand to lose voters to right-wing populist challengers are more likely to accommodate in anticipation of this electoral threat, an observational estimate of the effect of accommodation on mainstream left electoral support will be biased downwards. We take steps to address each of these challenges. With respect to the measurement of mainstream left success, we examine mainstream left party support as well as support for the parties who have pledged to support a mainstream left party government. With respect to causal inference, we rule out endogeneity by experimentally manipulating voters’ perceptions of mainstream left party positions on immigration in a context of positional ambiguity.

Empirical Setting & Research Design We conduct a survey experiment in the aftermath of Denmark’s general election on June 5, 2019. Announced a month earlier by the incumbent Prime Minister of the center-right Liberal Party, the election ended four years of governance by ﬁrst a single-party Liberal Party government and later a multiparty right-wing coalition. Throughout, the center-right government relied on support in parliament from the right-wing populist Danish People’s Party. The Social Democrats’ candidate for Prime Minister, Mette Frederiksen, had signalled a shift to a more restrictive position on immigration when taking over leadership of the party

3 four years earlier. This positional shift was significant enough to be picked up by international media (e.g., Milne, 2019). The incumbent Liberal Party made immigration salient in the campaign by questioning the credibility of the Social Democrats’ shift, appealing to voters’ memories of the most recent era of Social Democratic government, 2011-15, in which the Social Democrats had made considerable policy concessions to the centrist Social Liberals, effectively reneging on several key campaign promises (Bille, 2013). The election result, while delivering a sizable parliamentary majority to the parties supporting a Social Democratic Prime Minister, saw a small decline in support for the Social Democrats and a considerable gain for the relatively pro-immigration Social Liberals. As a result, the 2019 election saw the mainstream left return to power in Denmark, but left residual ambiguity about whether the Social Democrats’ proclaimed tougher immigration stance would be fully reflected in policy. We situate our survey in this context, fielding a nationally representative survey experiment in the short interval between election day and the official formation of a single party minority Social Democratic government supported by the Social Liberals and two socialist parties. Appendix B reports results from a content analysis of news stories in this period, showing considerable media attention to the incoming government’s immigration policy, but uncertainty about its position. We partnered with YouGov, a private polling firm, who conducted the survey on June 14-17, 2019, recruiting 2,016 respondents with the Danish voting–age population as the target population. The timing of our experiment addresses a recurrent challenge in research on party position taking, namely that parties tend to have stable policy reputations, making it difficult to observe outcomes of interest under alternative policy reputations. Some earlier studies address this challenge by observing voters before and after shifts in party position (e.g., Slothuus, 2010). However, this approach requires the researcher to either foresee a shift in party position or fortuitously field a panel survey shortly before a shift. Moreover, even this design remains vulnerable to confounding by simultaneous changes in the political environment not attributable to the change in party position. Alternatively, some studies use an experimental

4 design that randomly assigns positions to parties. However, party reputations often limit the set of credibly manipulable issues to less salient issues, where voters are unsure about parties’ positions (Slothuus, 2016). Unlike these studies, we are able to credibly manipulate a party’s position on the highly salient issue of immigration by exploiting the transitional policy ambiguity before the formation of the new government. The experimental component of the survey randomly assigns respondents to one of three conditions. In the control condition, we inform respondents that the Social Democrats are negotiating with other left-wing parties about the immigration policy of the coming government. In the first of the two treatment conditions, we then tell respondents that “observers” believe the Social Democrats will continue the restrictive immigration policy of the previous government. In the other treatment condition, the “observers” believe that the Social Democrats will set a less restrictive immigration policy. To ensure credibility of the treatments, we back up each treatment message with a paraphrased quote from the leader of the Social Democrats. Following Meguid (2005), we label the first treatment accommodative and the latter adversarial. (Meguid identifies a third strategy, dismissive, which we bracket here, focusing on the positional distinction between accommodation and adversarialism). Appendix C presents the experimental conditions in full with English translations. We examine the effect of the treatments on three outcomes of interest. First, we ask respondents to rate the restrictiveness of the Social Democrats on immigration policy on a 0-10 scale. This manipulation check allows us to assess whether the treatments successfully altered respondents’ perceptions of the party’s stance on immigration. Second, we ask respondents to rate their propensity to vote for the Social Democrat in light of the government negotiations on a 0-10 scale. Finally, we measure vote intention for the coalition of parties supporting a Social Democratic government, called the left bloc, by asking respondents about their vote choice if an election were held tomorrow. We recode responses into a binary indicator for choosing a party of the left bloc. The theoretical argument for why accommodation should work is underpinned by a spatial

5 model of voter behavior, implying that accommodation increases the Social Democrats’ electoral appeal among anti-immigration voters and decreases the appeal among pro-immigration voters. To test this implied mechanism, we estimate the effect of accommodation across two moderators: respondents’ anti-immigration attitude and their voting history. We measure anti-immigration attitude by asking respondents before the experimental treatments whether they consider immigration “a threat to Danish culture”, and whether Denmark “should take in more refugees compared to today”. We combine these two variables into an anti- immigration attitude index (Cronbach’s α=.83). We measure former vote choice by asking respondents before the experimental treatments about their vote choice in the 2015 general election, grouping answers into three categories: left bloc parties, Danish People’s Party (DPP), and other right bloc parties. If the effect of accommodation is driven by attracting anti-immigration voters, we should expect the effect to be concentrated among voters highest in anti-immigration attitudes and voters who supported the DPP in the previous election. Because the treatments are randomly assigned, the experimental groups are balanced on all pre-treatment variables in expectation. Experimental methodologists disagree on the appropriateness of testing for balance and adjusting for pre-treatment covariates (see e.g., Mutz and Pemantle, 2015). In the interest of full transparency, we present all estimates in bivariate model specifications (in black) as well as covariate-adjusted for past vote, education, age and gender (in gray). All dependent variables are recoded to go between zero and one.

Results Panel (a) of Figure 1 shows that our treatments credibly aﬀect respondents’ perception of the Social Democratic Party’s position on immigration (p < .01 for all pair-wise comparisons). If we compare respondents who were exposed to the accommodative and adversarial treatment, the former thought the respondents were roughly 0.1 scale points tougher on immigration, corresponding to ten percent of the full scale or half a standard deviation. Panel (b) shows that both the adversarial and accommodative treatments increased propensity to vote for the Social Democrats compared to the control condition (p < .1 and p < .05 respectively). This

6 is unexpected, but might be a result of some voters being more willing to vote for the party when uncertainty about their position on immigration is reduced one way or the other. Panel (c) shows that the accommodative strategy has a positive effect of voting for the left bloc as a whole. Depending on specification, respondents exposed to accommodation are between 3.5 and 5 pp more likely to support the left bloc than respondents exposed to the adversarial treatment (p < .1). The effect is modest, but substantively significant relative to the 4.9 pp total change in support for the left bloc between the 2015 and 2019 elections. In sum, while accommodation does not increase support for the Social Democrats relative to the adversarial strategy, the accommodation strategy does increase support for the left bloc as a whole, increasing the chances of a Social Democratic government. Examining heterogeneous effects in panel (a) of Figure 2, it becomes apparent why there is no effect on propensity to vote for the Social Democrats of being exposed to the accommodative rather than the adversarial treatment. Consistent with the spatial model, accommodation significantly increases support for the Social Democrats among anti-immigration respondents, and significantly decreases support among pro-immigration respondents (p < .01). Turning to left bloc vote intention in panel (b) of Figure 2, we find that the gains are concentrated among those who voted for the DPP in the last election. In fact, former DPP voters are between 8 and 9 pp more likely to vote for the left bloc when exposed to an accommodating rather than an adversarial Social Democratic party, though the effect is significant only with covariate adjustment (p = .12 and p = .07 respectively). Importantly, there is no sign of a reduction in the vote share among those who voted for the left bloc at the last election. Contrary to the result for Social Democrats PTV, there is no evidence that the effect of the accommodative treatment on left bloc vote intention is moderated by anti-immigration attitudes. Appendix D presents estimates from the linear regression models underlying these figures. In Appendices E and F, we show that the linear interaction effect assumption holds and that we obtain similar results with respect to left-bloc voting using logistic regression.

7 Manipulation check Social Democrats propensity to vote Left bloc vote intention

0.08 0.100

0.10 ● ● 0.075 0.04 ●

● 0.05 0.050 0.00 ● ● ● ● ● 0.025 0.00 ● ● ● −0.04 Effect on left bloc vote intention vote on left bloc Effect Effect on Social Democrats PTV on Social Democrats Effect

Effect on perceived SD restrictiveness on perceived Effect 0.000 −0.05 Adversarial Accommodative Adversarial Accommodative Adversarial Accommodative

(a) (b) (c)

Figure 1: Manipulation check (panel a), effects of treatment conditions on PTV for Social Democrats (panel b), and effects on left bloc vote intention (panel c). Covariate-adjusted estimates in gray. Error bars represent 90 and 95 pct. confidence intervals respectively.

Social Democrats propensity to vote

0.2 ● 0.1 ●

● ● ● ● ● ●

● ● 0.1 ● 0.0 ● ● ● ● ● Effect on PTV Effect Effect on PTV Effect ● ● ● ● ● 0.0 −0.1 ● ● ●

−0.1 0.00 0.25 0.50 0.75 1.00 Left bloc Other right DPP Anti−immigration attitude Former vote choice (a) Left bloc vote intention

0.15 0.2

0.10

0.1 ● ● ● 0.05 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.0 0.00 ● ● Effect on left bloc vote intention vote on left bloc Effect Effect on left bloc vote intention vote on left bloc Effect −0.05 −0.1

0.00 0.25 0.50 0.75 1.00 Left bloc Other right DPP Anti−immigration attitude Former vote choice (b)

Figure 2: Eﬀect of accommodation treatment on PTV for Social Democrats (panel a) and left bloc vote intention (panel b), compared to adversarial treatment. Covariate-adjusted estimates in gray. Error bars represent 90 and 95 pct. conﬁdence intervals respectively.

8 Conclusion Using a survey experiment in a rare setting of ambiguity about the mainstream left party’s position on immigration, we have shown that accommodating right-wing populist parties by taking a more restrictive position on immigration can increase mainstream left party support as well as support for the left bloc as a whole. While accommodation does cost votes among pro-immigration voters, these voters tend to defect to other parties on the left which typically support a mainstream left government. Moreover, accommodation attracts former supporters of populist right-wing parties in particular. While the mainstream left’s position on immigration was uniquely ambiguous in the setting studied here, the broader political context is quite typical. Mainstream left parties often have prospective coalition parties that are further left on immigration, to whom voters turned off by an accommodative strategy can turn without hurting the prospects for a mainstream left government (for evidence of this, see Appendix A). Even so, our findings are contextually specific in important respects. For example, while multiparty systems are relatively common, our finding may not generalize to two-party systems, where pro- immigration voters disaffected by an accommodating mainstream left party cannot defect to another left wing party. Moreover, while we find that accommodation can be effective, party systemic and institutional factors plausibly condition this relationship. Understanding this conditionality is an important topic for future research.

References

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10 Appendix (for online publication)

Appendix A Social Democratic governments with left-wing support 2

Appendix B Media coverage of Social Democrats’ position 4

Appendix C Experimental treatments 6

Appendix D Regression tables 7

Appendix E Test of linear interaction eﬀect assumption 10

Appendix F Logistic regression models 11

1 Appendix A Social Democratic governments with left-wing sup-

port

To assess the frequency of mainstream left parties relying on other left-wing parties in government, we consulted the ParlGov database (D¨oringand Manow, 2019) which includes information on the composition of parliaments and governments for 37 countries, including all EU countries and most OECD countries. For each country, we examined all governments which were led by a Social Democratic party since the year 2000. This came out to 97 governments across 28 countries. For those governments with coalition partners, we coded whether at least one of the coalition partners were left-wing, right-wing or both. To identify whether a coalition partner was left-wing

or right-wing we use the left right variable from the ParlGov database, representing the left-right position of the party on a continuous scale from 0-10. We identify a party as right-wing if it scores above 5 and left-wing if it scores below 5. Of the 97 Social Democratic governments, 22 were single party governments, 33 had at least one left-wing coalition partner and no right-wing partners, 17 had at least one right-wing and no left-wing partners, and 25 had coalition parties from both ends of the political spectrum. Figure A1 shows the distribution of cabinet types across the 97 cases. If we look broadly at Social Democratic governments the past 20 years, at least 34 percent of them would thus be in a situation similar to the Danish Social Democrats in 2019, where they could see an advantage of moving right on immigration, leaving pro-immigration voters to support other left-wing parties while attracting anti-immigrant voters from right-wing parties. In addition to this, any Social Democratic single-party minority government reliant on support from more left-wing parties in parliament would be in a similar situation. However, since we do not have any ﬁrm data on such informal coalitions, we cannot say how common this is.

2 Social Democratic−led governments by cabinet composition

Left and right Left only Right only Single party govt.

Figure A1: Distribution of cabinet types for 148 Social Democratic governments across 31 OECD and EU countries since 2000.

3 Appendix B Media coverage of Social Democrats’ position

To substantiate our claim that the Social Democrats’ position on immigration was salient and uncertain during the government negotiations, we conduct a content analysis of how the negotiations were covered in the news. We focus on ﬁve daily broadsheet newspapers, including both right-leaning (Jyllands- Posten, Berlingske, and Kristeligt Dagblad) and left-leaning newspapers (Politiken and Infor- mation). We target all articles that used the phrase “government negotiations” (“regerings- forhandlinger”) from the day after the election (June 6th, the start of the negotiations) until our data collection ended 12 days later (June 17th). In this period the six newspapers published 236 articles online and in print. Research assistants coded all these articles based on whether they mentioned the immigration issue, the issue of climate change or the issue of the economy. If the article mentioned the immigration issue it was coded for what (if any) prediction it made about the results of the negotiations (i.e., whether the article predicted that the Social Democrats would have to make meaningful concessions on immigration or not). Figure B1 shows the share of articles mentioning each of the three topics in the full set of 236 articles. Around one third of the articles (32 percent) were on the subject of immigration. This was more than the two other main points of contention in the negotiations, the economy and climate, which was mentioned in 28 and 17 percent of the articles respectively. Figure B2 shows the distribution of media predictions about the results of the negotiations. 12 percent of the immigration articles suggested that the Social Democrats would not make concessions to the left-wing parties they were negotiating with, 26 percent suggested that they would, and the remaining 62 percent made no predictions one way or the other. In analyzing the media coverage, we can thus conclude that immigration was a dominant issue in the negotiations, and that there was disagreement in the media about whether the Social Democrats would have to make meaningful concessions on immigration.

4 30

10 Share of articles mentioning topic (pct.)

Immigration Economy Climate change

Figure B1: Share of articles mentioning each policy area in media coverage of government negotiations.

Media predictions about Social Democrats' immigration policy concessions (pct.)

Concessions No concessions No prediction

Figure B2: Distribution of media predictions about Social Democrats’ policy concessions to other left parties on immigration. Based on content coding of 95 news stories in daily broadsheet news media during the government negotiations.

5 Appendix C Experimental treatments

Table C1: Experimental treatments with Enlish translations

Condition Original text English translation

Control Socialdemokratiet forhandler lige nu med The Social Democrats are currently nego- Radikale Venstre, SF og Enhedslisten tiating with the Social Liberals, the So- om, hvilken udlændingepolitik en ny cialist People’s Party, and the Red/Green socialdemokratisk ledet regering, med Alliance about what kind of immigration Mette Frederiksen som statsminister, skal policy a Social Democrat government, føre. with Mette Frederiksen as Prime Min- ister, should lead.

Accommodative Control text + Iagttagere peger p˚a, Control text + Observers point out that at Socialdemokratiet vil videreføre den the Social Democrats are expected to con- stramme udlændingepolitik, som den tinue the restrictive immigration policy of tidligere regering førte. Blandt andet har the former government. Like the former Socialdemokratiet ligesom den tidligere government, the Social Democrats have regering afvist, at Danmark igen skal tage refused to accept quota refugees. The imod kvoteﬂygtninge. Socialdemokrati- leader of the Social Democrats, Mette ets formand, Mette Frederiksen, har selv Frederiksen, has herself argued for a re- argumenteret for en stram udlændinge- strictive policy. For example, she has said politik. Hun har blandt andet tidligere that it is necessary to tighten immigra- udtalt, at det er nødvendigt at stramme tion law to ensure that the Danish society op p˚audlændingeomr˚adetfor at sikre at will be able to function properly in the det danske samfund kan fungere i fremti- future. den.

Adversarial Control text + Iagttagere peger p˚a,at Control text + Observers point out that Socialdemokratiet kommer til at føre the Social Democrats are expected to en mindre stram udlændingepolitik end set a less restrictive immigration policy den tidligere regering. Blandt andet than the former government. The So- har Socialdemokratiet ˚abnetfor, at Dan- cial Democrats have proposed accepting mark igen skal tage imod kvoteﬂygtninge, quota refugees, which the former govern- som den tidligere regering afviste. So- ment refused. The leader of the Social cialdemokratiets formand, Mette Fred- Democrats, Mette Frederiksen, has her- eriksen, har selv argumenteret for en min- self argued for a less restrictive immigra- dre stram udlændingepolitik. Hun har tion policy. For example, she has said blandt andet tidligere udtalt, at Danmark that Denmark should focus more on inte- skal have mere fokus p˚aintegration og gration and less on the number of refugees mindre fokus p˚ahvor mange ﬂygtninge, coming to Denmark. der kommer til Danmark.

6 Appendix D Regression tables

Table D2: Models of propensity to vote for Social Democrats

Perceived SD pos. SD PTV Left bloc vote int Intercept 0.55∗∗∗ 0.50∗∗∗ 0.37∗∗∗ 0.69∗∗∗ 0.44∗∗∗ 0.75∗∗∗ (0.01) (0.02) (0.02) (0.03) (0.02) (0.04) Accommodative treatment 0.05∗∗∗ 0.04∗∗∗ 0.06∗∗∗ 0.04∗∗ 0.07∗∗ 0.03 (0.01) (0.01) (0.02) (0.02) (0.03) (0.02) Adversarial treatment −0.03∗∗ −0.04∗∗∗ 0.04∗ 0.03∗ 0.02 −0.01 (0.01) (0.01) (0.02) (0.02) (0.03) (0.02)

Covariate adjustment XXX Adj. R2 0.02 0.13 0.00 0.28 0.00 0.42 Num. obs. 1809 1809 1755 1755 2016 2016 RMSE 0.23 0.22 0.37 0.31 0.50 0.38

∗∗∗p < 0.01, ∗∗p < 0.05, ∗p < 0.1

7 Table D3: Interaction models: Social Democrats PTV

Moderator: anti-imm. att. Moderator: frmr. vote Intercept 0.50∗∗∗ 0.73∗∗∗ 0.21∗∗∗ 0.18∗∗∗ (0.03) (0.04) (0.03) (0.05) Anti.immigration −0.15∗∗∗ −0.02 (0.05) (0.04) Control −0.09∗∗ −0.08∗∗ −0.01 −0.01 (0.04) (0.04) (0.05) (0.05) Accommodative −0.09∗∗ −0.10∗∗∗ 0.14∗∗∗ 0.14∗∗∗ (0.04) (0.04) (0.05) (0.05) Anti-imm.×Control 0.09 0.09 (0.07) (0.06) Anti-imm.×Accommodative 0.19∗∗∗ 0.20∗∗∗ (0.07) (0.06) Left bloc 0.36∗∗∗ 0.39∗∗∗ (0.04) (0.04) Other right 0.04 0.07 (0.04) (0.05) Left bloc×Control −0.04 −0.05 (0.06) (0.06) Left bloc×Accommodative −0.17∗∗∗ −0.17∗∗∗ (0.06) (0.06) Other right×Control −0.01 −0.02 (0.06) (0.06) Other right×Accommodative −0.12∗ −0.12∗ (0.06) (0.06)

Covariate adjustment XX Adj. R2 0.01 0.28 0.16 0.18 Num. obs. 1750 1750 1543 1543 RMSE 0.37 0.31 0.34 0.34

∗∗∗p < 0.01, ∗∗p < 0.05, ∗p < 0.1

8 Table D4: Interaction models: Left bloc vote intention

Moderator: anti-imm. att. Moderator: frmr. vote Intercept 0.86∗∗∗ 0.98∗∗∗ 0.09∗∗ 0.01 (0.04) (0.05) (0.04) (0.05) Anti.immigration −0.68∗∗∗ −0.37∗∗∗ (0.05) (0.05) Control 0.00 0.02 0.00 0.01 (0.05) (0.04) (0.05) (0.05) Accommodative 0.06 0.03 0.08 0.09∗ (0.05) (0.04) (0.05) (0.05) Anti-imm.×Control −0.02 −0.03 (0.07) (0.06) Anti-imm.×Accommodative −0.04 −0.01 (0.07) (0.06) Left bloc 0.70∗∗∗ 0.70∗∗∗ (0.04) (0.04) Other right 0.07 0.07 (0.05) (0.05) Left bloc×Control 0.02 0.02 (0.06) (0.06) Left bloc×Accommodative −0.03 −0.04 (0.06) (0.06) Other right×Control 0.00 −0.01 (0.06) (0.06) Other right×Accommodative −0.11 −0.12∗ (0.07) (0.07)

Covariate adjustment XX Adj. R2 0.21 0.46 0.46 0.46 Num. obs. 1987 1987 1685 1685 RMSE 0.44 0.37 0.37 0.37

∗∗∗p < 0.01, ∗∗p < 0.05, ∗p < 0.1

9 Appendix E Test of linear interaction eﬀect assumption

Figure E1 presents a test of the linear interaction effect assumption (LIE), as presented in Hainmueller et al. (2019), for the statistically significant interaction between the accomodation treatment and the propensity to vote for the Social Democrats. The figure was created using the interflex package for R. As shown, the marginal effect increases linearly along the moderator, showing that the linear interaction effect assumption holds.

Social Democrats propensity to vote 0.10 L M H

0.05 ●

0.00 ● ●

Effect on PTV Effect −0.05

−0.10

0.00 0.25 0.50 0.75 1.00 Anti−immigration attitude

Figure E1: Marginal eﬀect of the accommodation condition on Social Democrats PTV across the observed range of anti-immigration attitudes.

10 Appendix F Logistic regression models

Table F1: Logistic regression models for left bloc vote intention

Left bloc vote int Intercept −0.26∗∗∗ 1.11∗∗∗ (0.08) (0.25) Accommodative treatment 0.28∗∗ 0.18 (0.11) (0.15) Adversarial treatment 0.07 −0.06 (0.11) (0.14)

Covariate adjustment X BIC 2800.78 2044.95 Log Likelihood −1388.98 −915.95 Deviance 2777.95 1831.90 Num. obs. 2016 2016

∗∗∗p < 0.01, ∗∗p < 0.05, ∗p < 0.1

11 Table F2: Logistic regression interaction models: Left bloc vote intention

Moderator: anti-imm. att. Moderator: frmr. vote Intercept 1.64∗∗∗ 2.80∗∗∗ −2.37∗∗∗ −2.95∗∗∗ (0.19) (0.35) (0.35) (0.45) Anti-immigration −3.13∗∗∗ −2.52∗∗∗ (0.29) (0.37) Control 0.03 0.20 0.02 0.07 (0.27) (0.33) (0.48) (0.48) Accommodative 0.34 0.30 0.76∗ 0.85∗ (0.27) (0.33) (0.44) (0.45) Anti-imm.×Control −0.16 −0.23 (0.42) (0.50) Anti-imm.×Accommodative −0.31 −0.15 (0.43) (0.51) Left bloc 3.66∗∗∗ 3.70∗∗∗ (0.38) (0.38) Other right 0.65 0.67 (0.41) (0.42) Left bloc×Control 0.13 0.14 (0.52) (0.53) Left bloc×Accommodative −0.41 −0.49 (0.49) (0.49) Other right×Control −0.00 −0.05 (0.57) (0.58) Other right×Accommodative −0.98∗ −1.07∗ (0.55) (0.56)

Covariate adjustment XX BIC 2331.49 1894.26 1539.71 1599.89 Log Likelihood −1142.96 −829.42 −736.42 −725.65 Deviance 2285.92 1658.83 1472.84 1451.30 Num. obs. 1987 1987 1685 1685

∗∗∗p < 0.01, ∗∗p < 0.05, ∗p < 0.1

12 Appendix references

D¨oring,Holger and Philip Manow (2019). Parliaments and governments database (ParlGov): Information on parties, elections and cabinets in modern democracies. Stable version. Hainmueller, Jens, Jonathan Mummolo, and Yiqing Xu (2019). “How much should we trust estimates from multiplicative interaction models? Simple tools to improve empirical practice”. In: Political Analysis 27.2, pp. 163–192.