Why do electoral systems change? Accounting for parties, institutions and voters: evidence from the deviant case of Italy

Abstract Electoral system change is often explained as a strategic response to party-system fragmentation, but changes in the effective number of parties (ENP) alone cannot account for repeated shifts in electoral rules in the Italian case. This article analyses Italy as a deviant case to refine theories of electoral system change by incorporating the interaction between parties, voters, and institutions. Using process tracing, it reconstructs the three main reform episodes (1993, 2005, 2017) and identifies the mechanisms through which each actor shaped the feasible set of electoral system outcomes. The findings show that parties’ strategic payoffs and coalition incentives are not sufficient: citizen mobilisation constrains elite bargaining, while judicial review and technocratic intervention can act as catalysts and hard constraints that redirect reforms toward constitutionally viable compromises. The analysis suggests that Italy is increasingly unlikely to return to a pure proportional model or to adopt a durable majoritarian system; instead, mixed systems persist as the most feasible equilibrium between electoral competition, public legitimacy, and constitutional constraints.