Rebels in Parliament: The Effects of Candidate Selection Methods on Legislative Behaviours.

This article examines whether candidate selection methods influence the likelihood of members of parliament (MPs) defecting from their party line, focusing on the Italian Democratic Party (Partito Democratico—PD) during the XVII legislature (2013–2018). The PD provides a unique case as its MPs were selected both through inclusive semi-open party primaries and exclusive party leader appointments within the same institutional context. The study finds that MPs chosen via inclusive primaries are significantly more prone to rebel votes compared to those nominated by party leaders, supporting the hypothesis that candidate selection shapes individual legislative behavior. Additionally, when the future selectorate shifted from primaries to party leadership, MPs reduced their defections, indicating that incentives tied to re-selection influence loyalty. The analysis also highlights that MPs with strong local ties exhibit greater independence from party discipline, underscoring the role of localism in Italian parliamentary behavior.