Studies on the PRI in the first five years of the 21st century.

The characteristics that defined the PRI in its long trajectory as a ruling party were inexplicably related to the presidentialist system of which it was its electoral political expression. This paper aims to rescue the attempts that have come closest to this objective and to show how, through the categorization of aspects, themes or problems, we can acquire a broader knowledge about this institution that prevailed during most of the last century.