In the 1980s and 1990s, economic crisis produced ideological convergence in many Latin American party systems. Much scholarship explores how this convergence frequently provoked system change that enabled renewed ideological differentiation, but little research examines instances where convergence persisted without destabilizing the system. Through comparative historical analysis of Dominican continuity amid regional change, this study identifies factors that sustain or challenge party systems. Then, through analysis of Americas Barometer surveys, it assesses the causal mechanisms through which these factors shape support for the traditional Dominican parties. The findings demonstrate that maintaining programmatic and clientelist linkages facilitates continuity. In addition, the article argues that the threats political outsiders pose to existing party systems are constrained when people excluded from the system are divided and demobilized. In the Dominican case, Haitian immigration divides the popular sector while Dominicans abroad sustain ties to the parties, with both migration flows facilitating party system continuity.