Primary elections for choosing party leaders and candidates are now becoming commonplace in Europe, Asia and America but questions as to how much they hinder a party’s organizational strength and cohesion or affect electoral performance have largely been ignored outside of the USA. Party Primaries in Comparative Perspective gives a much-needed conceptualization to this topic, describing the function and nature of primary elections and providing a comparative analytical framework to the impact of primaries on the internal and external functioning of political parties. Elaborating on the analytical tools developed to study the US experience this framework engages with primary elections in Europe and Asia offering a theoretical, comparative and empirical account of the emergence of party primaries and an invaluable guide to internal electoral processes and their impact.