This article explains variation in the electoral trajectories of Latin American traditional parties since transitions to democratic governments in the late 20th century until the first half of the 2000s, when democracies were already consolidated. This article addresses the question of why some parties suffer more than others under challenging contextual conditions, or why some parties are able to weather difficult external environments, e.g. economic crises, institutional reforms or political scandals, while others fail. This study argues that the internal organization of parties matters: it affects their ability to react and survive, especially in contexts of environmental change. Variation in parties’ internal characteristics explains different outcomes in their electoral performance. An empirical analysis of 48 traditional parties over almost three decades (1978–2006) provides support for this argument.