The article rebuilds the process of adaptation of the MLN-Tupamaros to legality and electoral competition since the restoration of democracy in Uruguay (March 1985) and the election of José Mujica, founder of the MLN-T and candidate of the Frente Amplio, as president of Uruguay (November 2005). This path is a particularly remarkable case of successful party adaptation. The central argument is that the remarkable adaptability of this organization must be explained mainly by some features of its ideological matrix which is distinguished, in the Uruguayan left, for his pragmatism.