Bértoa, Fernando CasalEnyedi, ZsoltMölder, Martin2025-03-242025-03-242024-03-171537-592710.1017/S1537592723002530https://hdl.handle.net/20.500.14018/26626Publisher Copyright: © The Author(s), 2023.Parties and party systems are treated as separate phenomena in theory, but not in research practice. This is most clearly so in the literature on the institutionalization of party politics, where the party level and the systemic levels are often analyzed through combined fuzzy indices. We 1) propose separate indicators for measuring institutionalization at the party and at the party system level, 2) demonstrate their different dynamics in twentieth and twenty-first century European countries, and 3) investigate the direction of causality. Using a dataset that covers more than 700 elections, 800 parties, and 1,400 instances of government formation in 60 different historical party systems across 45 European countries, we find that party-level institutionalization tends to precede systemic institutionalization. The opposite pattern occurs only in a few countries.enginfo:eu-repo/semantics/openAccessPolitical Science and International RelationsJournal articlehttp://www.scopus.com/inward/record.url?scp=85175446701&partnerID=8YFLogxKBértoa, F C, Enyedi, Z & Mölder, M 2024, 'Party and Party System Institutionalization : Which Comes First?', Perspectives on Politics, vol. 22, no. 1, pp. 194-212. https://doi.org/10.1017/S153759272300253019644139