This article compares Indonesia's party systems of the 1950s and the post-Suharto period. It explores the question of why the party system of the 1950s collapsed quickly, while that of the contemporary polity appears stable. Challenging established assumptions that party systems fail if their individual parties are weakly institutionalised, I submit that the fundamental difference between the party politics of the 1950s and today's democratic system is related to the character of inter-party competition in both periods. While inter-party contestation in the 1950s took place at the far ends of the politico-ideological spectrum, the competition between parties in the contemporary democracy exhibits centripetal tendencies, stabilising the political system as a whole.