espanolLa oposicion parlamentario/presidencial funda el discurso moderno de los regimenes politicos, dando lugar a la discusion sobre la �mejor� estructura de gobierno para el desarrollo de la democracia. Discusion que sera el eje conductor de uno de los debates mas ricos de la ciencia politica contemporanea. Los estudios sobre la materia han superado sucesivas etapas que pueden caracterizarse como sigue: 1) defensa de la superioridad absoluta de un modelo con base en los vicios intrinsecos del otro, que resultarian desfavorables para la estabilidad democratica (The best system approach); 2) relativizacion de las ventajas en abstracto del tipo de regimen mediante la explicacion de la fragilidad democratica por factores �exogenos� al modelo de gobierno; 3) replanteamiento de los terminos del debate a partir de la exploracion de los mecanismos de racionalizacion de los regimenes politicos. En la actualidad, el giro metodologico que opera el analisis cuidadoso del contexto (sistema electoral y de partidos, historia y costumbre constitucional) abre nuevos horizontes de investigacion al tiempo que recupera la importancia del debate para Latinoamerica, en tanto cuna y laboratorio historico del modelo presidencialista. EnglishThe opposite terms �parliamentarian� and �presidential� set the modern discourse of political regimes and open to discussion on �best� government structure for the development of democracy. This will lead to one of the most important debates in modern political science. Studies on the matter went through successive stages, which could be characterised as follows: 1) Defence of absolute superiority of a model based on intrinsic perversions of the other, which would harm democratic stability (The best system approach). 2) Relativization of the abstract benefits of the regime type explaining with �exogenous� factors to the model of government the weakness of democracy. 3) Re-examination of the terms of the debate from the exploration of the mechanisms of rationalization of political regimes. Currently, the methodological turn given by the careful analysis of the context (electoral and party system, constitutional history and custom) opens new research areas as well as underlines the importance of the debate for Latin America, both as historical source and laboratory of the presidential model.