Providing a definition built on the agency relationship between voters and public officials, this study presents an institutional approach to the causes of political corruption. I argue that higher levels of political party institutionalization reduce political corruption. Institutionalized political party systems help to overcome collective problems among voters within democracies. By increasing levels of accountability, institutionalized political party systems alter public officials\u27 incentives towards a cleaner exercise of the public power. Focusing on different strategies adopted by political parties, I analyze the effectiveness of the constraints imposed on public officials\u27 corrupt behavior within democracies. On the one hand, institutionalization of political party systems increases the incentives for political parties to monitor public officials\u27 performance due to their need to create and protect brand-name capital. On the
other hand, institutionalization of the political party systems, by supplying low cost information, allows the constituencies to exercise retrospective and prospective voting, strengthen credible commitments in sanctioning abuses in the public officials\u27 use of power. Characterization of the party system in terms of institutionalization demonstrates how having a democratic system does not ensure effectiveness of political controls against political corruption. The analysis provides a quantitative analysis based on a cross-national sample of eighteen Latin American countries, and a qualitative analysis of the causal relationship in Colombia
