The institutional design and the operation of state institutions are expressions of political culture in a society. As such, they are also indicators of the quality of democracy in terms of results. Within the transition and consolidation processes of democracy in Latin America, the design and operation of Electoral Management Bodies (EMB’s) have been of exceptional importance. In order to overcome lack of credibility towards elections -a result of authoritarianisms in many Latin-American countries- the independent EMB model reinforced by Electoral Courts to solve electoral quarrels has been widely promoted in Latin America. How can this choice be explained? Have independence and wide powers of EMBs in LA positively influenced sociopolitical trust towards elections? Focusing on the cases of Mexico, Brazil and Peru, this paper proposes a framework to comparative analysis of EMBs in LA, considering: a) levels of independence and; b) power capacity on electoral processes, as independent variables, and their impact on c) social trust and political credibility as result variable. It is the purpose to illustrate how EMBs design in these countries was influenced by the kind of transition taking place where lack of credibility turned them into a forth institutional power.