Why do parties cooperate in presidentialism? Electoral and government coalition formation in Latin America

Résumé

The purpose of this article is to explore coalition formation in presidential systems using evidence from Latin America. It puts forward three hypotheses based on formateur power, electoral structures and party systems to explore when and why electoral and government coalition formation occurs. It uses evidence stemming from eighteen democratic presidential regimes in Latin America from 1980 to 2010. It looks at 100 elections and 407 aggregate years of democratic government. It analyses data organized in a cross-sectional time-series fashion through a logit function with random effects and robust standard errors. It finds that in democracies with weak presidents, restrictive electoral rules and highly fragmented party systems, the president will seek the support of multiple parties. While the effective number of parties is the most important determinant, rules related to legislative elections are more important predictors of electoral coalitions, and those related to presidential elections are more important predictors of government coalitions. The findings in this article are important insofar as yielding critical insight into partisan strategies in both the run-up to elections and the maintenance of governments, as well as contributing to a general theory of coalition formation.