An overlooked revolution? Party system denationalisation in Western European multilevel election systems

This article argues that party system denationalisation in Western Europe has been underestimated due to methodological nationalism, which privileges national elections and parties as units of analysis. Regional election data from fourteen multilevel democracies since 1950 is used to uncover growing divergence between regional and national election outcomes, indicating substantial denationalisation despite stability detected by convential indicators. Appropriately revised measures incorporating regions and regional elections reveal that approximately one in five voters supports different parties across electoral arenas. Four types of territorial effects – nationalised, mediated, isolated, and coinciding – are conceptualised to clarify how subnational and national stimuli shape electoral outcomes. An application of this conceptual framework reveals that regional, regionalist, and new parties increasingly drive electoral differentiation and likely contribute to party system renewal at the national level. Moving beyond methodological nationalism improves the understanding of multilevel representative democracy and highlights the importance of territorial agency in shaping electoral competition.