Populism is a contradictory phenomenon. Great singularities mark its history in South America. This paper will try to register the diversity of circumstances that applies to the countries of the area, for later on to concentrate its efforts in the analysis of the populism. The conclusions go beyond the particularities of thepopulism, phenomenon associated so much to authoritarian regimes as to democratic ones, in the left or right wings, with a cultural convergence in favor of antagonisms that produce a decadence of the political community as a whole. In this sense, the main effect of the populism is to hinder the institutions of liberal democracy.