Going It Alone? A Structural Analysis of Coalition Formation in Elections

The quality of democratic representation hinges on the alternatives available to voters. In many democracies, party leaders exercise considerable control over the electoral supply, particularly through the formation of electoral coalitions. Despite their prevalence, little is known about the tradeoffs these coalitions impose on prospective partners, how they influence other strategic choices by competing parties, or their ultimate impact on election outcomes. I develop and estimate a model of electoral competition in which (i) parties can form coalitions to coordinate their candidate nominations and (ii) parties invest in campaign activities in support of their candidates. The model is estimated using data from the 2012 Mexican Chamber of Deputies election, which offers district-level variation in coalition formation. A comparison of election outcomes under counterfactual coalition scenarios uncovers equilibrium campaign savings as well as significant electoral gains benefiting weaker partners disproportionately.