This research challenges conventional wisdom in comparative political behavior in two important ways. It finds that partisanship in Latin America is not as weak as prior comparative studies have suggested. In fact, this research finds that the proportion of partisans was underestimated by major comparative surveys. Additionally, this dissertation finds that partisans are not as vulnerable to campaign information as previously considered. Even in new democracies, partisans reinforce their prior beliefs while rejecting information that is inconsistent with their partisan predispositions. In these contexts, campaigns play a major role in "enlightening" voters by providing them with information to support the candidate most in line with their pre-campaign political predispositions.