Constraining the Party Elite: Congress Power and Party Responsiveness to Voters

Understanding why some parties are more responsive to voter preferences than others remains a central concern in the study of representation. A prominent line of research emphasizes the role of intra-party organization, arguing that parties in which decision-making is less concentrated in elite hands should be better able to translate societal preferences into policy positions. Yet empirical evidence on this relationship remains weak or inconclusive, in part because existing measures of intra-party power are imprecise and largely time-invariant, limiting our ability to capture meaningful institutional change within parties. This paper advances the study of party responsiveness by focusing on the institutional power of party congresses, the formally highest decision-making bodies in most parties and key arenas for member influence. Building on theories of intra-party democracy and party responsiveness (e.g., Lehrer 2012; Bischof and Wagner 2020), we argue that more powerful congresses constrain elite discretion and strengthen the transmission of preferences from party members and activists to party policy. This, in turn, should increase ideological congruence between parties and their voters. To test this argument, the paper introduces a new Party Congress Power Index (PCPI) based on original annual coding of party statutes and standing orders for 20 parties in Germany, the Netherlands, and the United Kingdom from 1990 to 2022. The index captures four dimensions of congress power—tasks, impact, independence, and legitimacy—and allows for the first longitudinal analysis of formal congress authority. By providing a dynamic, institution-level measure of intra-party power, the paper contributes to unresolved debates about how organizational rules shape party responsiveness over time.