At the beginning of the 1990’s the Mexican political system seemed to be entering a pattern of political unpredictability from which it had excaped in the past. The origins of this new situation can be traced back to the 1980’s when the country faced on economic crisis of unprecedented dimensions. The policies of economic adjustment and restructuring of the State found an important echo in the political sphere. The weakening of State interventionism brought about a loosening of traditional political controls that opened the door to independent political mobilization and liberalization. But this process has also awakened populism, a deeply rooted political tradition with which many Mexicans still identify. Thus, in Mexico, the main threat to political change comes from its own populist past which was for years a solid pillar of authoritarianism.