My doctoral dissertation begins with this puzzle: why do large, moderate parties sometimes select leaders who seem to help improve their parties' electoral performances, but other times choose unpopular leaders with more extreme policy positions, in expense of votes? I argue that leadership selection is dependent on both the electoral institution that a party finds itself in and the intra-party dynamics that constrain the party. Due to a high degree of seat-vote elasticity that is characteristic of majoritarian systems, replacing unpopular leaders is a feasible strategy for opposition parties in these systems to increase their seat shares. In contrast, in proportional systems, due to low seat-vote elasticity, on average opposition parties that replace their leaders suffer from vote loss. My model of party leadership selection shows that since party members can provide valuable election campaign effort, they can coerce those who select the party leader (the selectorate) into choosing their preferred leader. When selectorate members are moderate, extreme leaders may emerge if non-selectorate members credibly threaten to withhold campaign effort. The more that the extreme non-selectorate members value issue advocacy over the party's electoral welfare, the more extreme the chosen party leader is.
Two original datasets on 12 parliamentary democracies of the Organisation for Economic Co-Operation and Development (OECD), one comprised of the dates of party leadership tenure, and the other on leadership election results, highlight my research question's empirical relevance. These data reveal that on average, new opposition party leaders in single-member district (SMD) systems increase their parties' vote share, but the reverse occurs in multi-member district (MMD) systems. Through field research in the Netherlands, Sweden, and the United Kingdom, I interviewed 72 members of parliament (MPs), 7 former party leaders and party leadership candidates, and 18 senior party officers. These interviews serve to support my model's predictions.
My dissertation offers an explanation for why parties sometimes seem to injure themselves in the electoral arena by choosing unpopular leaders. It underscores the importance of electoral systems in understanding the dynamics of intra-party politics and the feasibility of different electoral strategies. In addition, intra-party policy conflict influences election outcomes. Moreover, it highlights how, paradoxically, large parties that prioritize their parties' electoral welfare sometimes sacrifice voter representation in order to mobilize party activists.