All on board? The role of institutional design for public support for differentiated integration

Differentiated integration is often considered a solution to gridlock in the European Union. However, questions remain concerning its perceived legitimacy among the public. While research shows that most citizens are not, in principle, opposed to differentiated integration - although support varies across different differentiated integration models and different country contexts - we still know little about the role institutional design plays in citizens' evaluations of differentiated integration. This article inspects how citizens evaluate different hypothetical differentiated integration arrangements, with varying decision-making procedures, using a conjoint experiment. We ask whether institutional arrangements can overcome citizens' preference heterogeneity over differentiated integration, and thereby foster the legitimacy of a differentiated European Union. We find that while a majority of citizens care about the inclusiveness of differentiated integration arrangements, they also support limiting the number of veto points. Our analysis also reveals noteworthy differences across citizens with pro- and anti-European Union attitudes in the perceived fairness of differentiated integration arrangements.