This book analyzes the transformation of the Mexican political system during the last four decades seen through the lens of its presidential elections. In the 1970s, Mexican presidential elections were without choice; thirty years later, the number of candidates and the competition increased dramatically to multiple parties and candidates. How can we classify presidential elections in Mexico between 1976 and 2012? How should these complex processes and the behavior of the Mexican electorate be explained? This monograph uses a mixed methodology including historical and statistical analysis of the presidential elections in Mexico to address these questions. In its chapters, the project presents a typology of presidential elections generally followed by detailed analysis of the presidential elections between 1976 and 2012.