What explains ideological congruence between citizens and political parties? Although the literature on congruence has recently provided some answers to this question, most of these works have focused on the effect of systemic and partisan factors. They have paid less attention to the effect of people’s characteristics on ideological congruence, which is built by the interaction between citizens’ positions on public issues and those of the political parties that represent them. Our general research hypothesis is that party-voter congruence is stronger when parties reduce the uncertainty about their ideological positions and citizens can understand these signals better. Analysis of Latin American data supports this hypothesis, showing that people’s cognitive ability, specifically education and political knowledge, has a positive effect on party-voter ideological congruence. Moreover, this relationship is moderated by parties’ attributes, such as ideological ambiguity and radicalism.