How does a party’s organizational structure affect its chances of becoming a national party? While existing explanations of party nationalization focus on country-level institutional and societal variables, we argue that aspects of party organization such as the degree of centralization of authority, ideological unity and leadership factionalism also matter. By bringing the analysis to the party level, this article provides a multilevel analysis of institutional and party organization variables and disentangles the effect of each set of influences. We use original data on party organization and party nationalization for 142 parties across twenty European countries. This research contributes to the literature on nationalization and party development by advancing organizational strategies which parties could adopt in different social and institutional environments.
