This thesis examines the relationship between the political opposition and populism. The goal is to identify when, how, and under what circumstances an opposition to a populist leader affects change to the political system. A comparative historical analysis is employed as five case studies from South America are examined. The evidence presented in these case studies demonstrates that the political oppositions in each country were unsuccessful in affecting change to their respective political systems. They were unable to demobilize the support base that the populist leaders had created. Change came to the political systems in four out of the five case studies only when the populist leader's actions demobilized his support and not from the actions of the opposition. / by Morgan Alissa Weiss. / Thesis (M.A.)--Florida Atlantic University, 2009. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2009. Mode of access: World Wide Web.