Comparative Effects of Electoral Reforms on Party System Change

Thesis Abstract

This study investigates how electoral reforms influence party system change across comparative contexts, addressing the problem of inconsistent empirical findings on volatility, party fragmentation, and alignment in new and mature democracies. The aim is to assess the causal and contextual pathways through which specific reform types—proportional representation, mixed-member systems, threshold adjustments, and candidate-list innovations—shape party systems in diverse institutional environments. Specific objectives include (1) identifying patterns of party-system change following reform episodes in six democracies over the past three decades; (2) evaluating the mediating roles of political culture, incumbency advantages, and media ecosystems; (3) testing the relative effectiveness of reform modalities in reducing or intensifying party fragmentation; and (4) developing a comparative framework to predict party-system responses to electoral reforms. The research adopts a comparative cross-national design, combining most-different-system and within-case longitudinal approaches. The population comprises established and transitional democracies that implemented substantial electoral reforms between 1990 and 2020. A purposive sample of twelve cases is analyzed, including Ireland, Hungary, New Zealand, Mexico, South Korea, and Spain, complemented by three transitional cases from Eastern Europe. The sample size yields a matrix of reform types and outcomes suitable for robust cross-case inference. Data collection triangulates official electoral data, party manifestos, parliamentary records, and media content from national archives and credible online databases, supplemented by 60 semi-structured elite interviews with party leaders, electoral officials, and political scientists conducted during field visits. Validity and reliability are ensured through triangulation, inter-coder reliability checks for content analysis, and pilot testing of interview protocols. Data analysis employs a mixed-methods approach quantitative time-series regression and event-history analysis examine changes in vote shares, seat shares, and effective number of parties pre- and post-reform, controlling for socioeconomic covariates and regime-type indicators; qualitative process tracing analyzes reform implementation, political bargaining, and institutional adaptation; and a comparative case-logic synthesis identifies contextual conditions under which reforms yield convergent or divergent party-system outcomes. Theoretical grounding integrates Duverger’s law and its modern extensions, Lijphart’s consociationalism, and the institutionalism of event-centered political economy to explain reform-induced realignments. A conceptual model links reform design to strategic actor behavior, institutional rules, and socio-political context, predicting pathway-specific outcomes such as fragmentation reduction under inclusivity-enhancing thresholds or unintended volatility under threshold instability. Anticipated findings indicate that proportional representation with moderate thresholds tends to consolidate moderate party systems by expanding viable coalitions, whereas extreme thresholds or frequent recalibration generate transient volatility and strategic lists, particularly in polities with strong party competition and media fragmentation. The study is expected to reveal varying effects across regime types mature democracies exhibit greater resilience to reform-induced disruption, while transitional systems show higher sensitivity to incumbent strategies and civil society engagement. The contribution to knowledge lies in a comprehensive, theory-informed comparative framework that consolidates disparate empirical results, clarifies the conditions under which electoral reforms catalyze party-system change, and provides a predictive tool for policymakers and scholars. The research recommends carefully calibrated reform packages that align institutional incentives with democratic deepening, gradual implementation with robust monitoring, and transparent stakeholder consultation to manage fragmentation dynamics. It concludes that a nuanced understanding of design features—threshold levels, the nature of the list, and transitional sequencing—combined with attuned institutional contexts, is essential for predicting and guiding desirable party-system outcomes in comparative democracies.