Political parties are now part of the “political scene”, indeed one of its essential elements. A democratic system without political parties or with a single party is impossible – or at any rate hard – to imagine. A dominant phenomenon of today, however, is the institutionalization of the political parties as powerful organizations that seek to monopolize mediation between the governed and those who govern. There are several aspects of the concept of party institutionalization. From a sociological point of view, it involves transforming associations that are structured to a greater or lesser degree into genuine organizations that are managed with a view to winning and exercising political power. This kind of institutionalization implies a combination of “objective” elements (the parties being firmly established as institutions) and “subjective” ones (acceptance of the parties, recognition of their legitimacy). From a more juridical point of view (inspired mainly by the ideas of Kelsen), institutionalization involves recognition for the political parties and their constitutional integration within the political system.