Comparative Politics with Endogenous Intra-Party Discipline1

Party discipline is known to be di¤erent in Parliamentary and in Presidential democracies. Yet, the theoretical literature is silent about why parties adopt such di¤erent structures. We propose a setup where parties are brands. They strategically choose both their ideological position and their internal discipline. The latter introduces a trade-o¤ between the informativeness of the party label and the candidates’legislative freedom. Our results show that parties never choose intermediate levels of discipline. In a system where “some”legislative discipline is valuable –in parliamentary regimes –parties prefer maximal discipline and moderate polarization. By contrast, when voters have su¢ ciently heterogeneous preferences, they prefer strong polarization and minimal discipline in presidential regimes. These …ndings also relate to the ‘dance’between polarization and inequality observed in the US and provide a novel explanation for why Duverger’s Law is more likely to hold in presidential than in parliamentary regimes.