Hans Kelsen is considered the most important exponent in the Philosophy of Law in the last century. His thought, however, remains influential in the current legal theory. But not only of legal matters has he treated. Besides them, Hans Kelsen dedicated much attention to the study of politics, especially to the inquiry of democracy and its conditions of empirical accomplishment. In order to do so, he deepened the studies concerning the epistemological assumptions of this regimen, with the intention to put in evidence the necessary - or adequate - philosophical requirements to its adoption. On the other hand, he analysed the main political discourses of his time, especially those related to liberalism and Marxist-Leninist socialism, trying to establish the compatibility of each one to the ideal democratic proposal. In this way he could single out the major points in which each of those doctrines gets closer or more distant to the corresponding democratic model, having had therewith the opportunity to verify, before the complex demands of contemporary societies, the fundamental requirements from which one can truly speak of a democratic regimen. This thesis discloses this path, presenting the key points that mobilized Hans Kelsen’s attention and his rich political thought.