Political Selection under Alternative Electoral Rules

We study the patterns of political selection in majoritarian versus proportional systems. Political parties face a trade-off in choosing the mix of high and low quality candidates: high quality candidates are valuable to the voters, and thus help to win the elections, but they crowd out the parties' most preferred loyal candidates. In majoritarian elections, the share of high quality politicians depends on the distribution of competitive versus safe (single-member) districts. Under proportional representation, politicians' selection depends on the share of swing voters in the entire electorate. We show that, as the share of competitive districts increases, the majoritarian system begins to dominate the proportional system in selecting high quality politicians. However, when the share of competitive districts becomes large enough, a non-linearity arises: the marginal (positive) effect of adding high quality politicians on the probability of winning the election is reduced, and proportional systems dominate even highly competitive majoritarian.