During the democratic post-transitions the Latín-American party systems faced the need of selftransformation, including new axes and dimensions to the inter-partisan competition in order to adapt to the demands established bythe traditional representative system deficits. As a consequence, new opposition
parties (challenging parties) emerged which presented themselves as alternatives to the traditional parties. The successfully established challenging parties (EP-FA, PAN, PRD, and PT) established clear patterns of competition against the political status quo, acquired strong social support, and presented organic and
newly institutional characteristics, while those that failed (AD-Ml9, FREPASO, LCR and MAS) did not achieve competition strategies that were consistent with the alternative represéntation that raised them, and they ended up dissolving away. Lastly I argue that the level of institutionalization of the party system
is related to the successes and failures of the challenging parties.