Play to your strengths: Incumbency effect and issue emphasis in Brazilian local elections

Incumbents’ reputations acquired during their time in office influence voters’ choices. Some studies suggest that, when designing their campaign messages, incumbents might benefit from playing to their strengths and emphasizing fewer issues than challengers. In this paper, I provide causal empirical evidence to support this hypothesis using information from mayoral elections in Brazil and a regression discontinuity design. The findings indicate that incumbency causes campaign manifestos to be more concentrated. Moreover, incumbents who belong to a cohesive and programmatic party tend to emphasize party-specific issues more. This suggests that reputation matters for issue selection. To measure issue emphasis and manifesto concentration, I leverage a unique database of more than 28 thousand documents containing political manifestos and use a Latent Dirichlet Allocation (LDA) algorithm to estimate a vector of topics – or the issues emphasized by each candidate. With this information, I calculate Herfindahl Hirschman Indices (HHI) for each manifesto to assess their relative issue concentration.