Electoral rules and political competition : regression discontinuity evidence from brazilian municipalities

Abstract

This paper uses exogenous variation in voting schemes to estimate the causal effect of different electoral rules on political competition, exploiting a regression discontinuity design in the assignment of single-ballot and dual-ballot plurality systems in Brazilian mayoral races. The results indicate that dual-ballot plurality rule causes an increase in political competition, decreasing the probability of reelection of the incumbent mayor (the personal incumbency advantage) and the vote share of winning candidate. In line with theoretical results, we find that evidence consistent with an increase in the number of parties and candidates as a possible mechanism behind these findings.