Article From staunch supporters to critical observers: Explaining the turn towards Euroscepticism among regionalist parties Emanuele Massetti School of International Studies and Department of Sociology and Social Research, University of Trento, Trento, Italy Arjan H Schakel Department of Comparative Politics, University of Bergen, Bergen, Norway Abstract Based on a new dataset, this article explains a turn towards Euroscepticism by region- alist parties from the early 2000s. Our findings point to the effects of cross-dimensional ideological linkages – positions adopted on the centre-periphery and left–right dimen- sions – and of an increasing formal regional involvement in European Union affairs without actual influence, which leaves regionalist (and especially secessionist) parties frustrated with the European Union multi-level system. Our findings substantiate the argument that regionalist parties are strongly supportive of economic integration but less supportive of political integration. They are also in line with the fall of the ‘Europe of the Regions’ thesis. Keywords European integration, Europe of the Regions, Euroscepticism, regionalist party, secessionism Corresponding author: Emanuele Massetti, School of International Studies and Department of Sociology and Social Research, University of Trento, Via Tommaso Gar 14, Trento 38122, Italy. Email: emanuele.massetti@unitn.it European Union Politics ! The Author(s) 2021 Article reuse guidelines: sagepub.com/journals-permissions DOI: 10.1177/14651165211001508 journals.sagepub.com/home/eup 2021, Vol. 22(3) 424–445