Partidos tradicionales y terceras fuerzas: una lucha por la relevancia en las elecciones a alcaldes en Colombia, 2015-2019

Objective/context: One goal of recent political reforms has been to expand the participation of new political forces; in the 2015 and 2019 local elections, third forces competed in every Colombian municipality, yet few achieved relevance vis-à-vis traditional parties; this study examines how and under what conditions third forces reshape the mayoral electoral market, distinguishing between organizations with national and local reach. Methodology: The study compiles municipal-level electoral and social data and estimates logistic regression models with cluster-robust standard errors at the municipality level; relevance is operationalized via the effective number of parties, and the national strength of third forces is constructed from their presence in representative bodies and elected offices at different levels. Conclusions: Third forces are more likely to be relevant when they are national political forces and, when they are, their relevance lowers the probability of victory for traditional parties; substantively, a one–standard deviation increase in the average national strength of third forces raises by 95.7% the likelihood that at least one is locally relevant. Originality: The study engages with debates on setbacks in political openness and decentralization, contributes an explicit measure of relevance based on electoral fragmentation, and shows that, despite the predominance of traditional parties and coalitions, third forces require organizational capacity and national anchoring to turn presence into subnational successes.