ABSTRACT
This paper explores external (country-level) and internal (party-level) drivers of membership variations across parties. Relying on the Political Party Database combined with other datasets, we provide original, cross-sectional analyses of membership variation across 223 parties in 38 countries, innovatively covering third-wave democracies, post-communist countries, and advanced democracies. It allows for a unique analysis of recruitment patterns of parties under quite different contexts. Departing from the dominant view that parties are the powerless victims of external trends, we show that, while context matters, parties’ choices regarding affiliation rules and organization structure also matter. They are more powerful determinants of membership ratios than country-level variables. Especially, the representation of sub-groups in the party structure is a key driver of membership recruitment. We also show how party origins, and the foundational environment in which they emerged, are important to understand how membership varies across parties today. Overall, this study strongly advocates for a broad comparative, multilevel approach to party membership.