During the years under the monopoly rule of the Partido Revolucionario Institucional (PRI) which lasted for 71 years, Mexico suffered authoritarianism, violence and economic crisis as witnessed in the 1968 student repression in connection with protests during the Olympic Games and the economic crisis beginning with the Latin American Economic Crisis in 1982 and culminating in 1994 with the devaluation of the Mexican Peso. At this time, there was a sentiment of governmental misrepresentation among the Mexican population. These actions highlight some of the important reasons why the PRI party was generally not seen as legitimate. The culmination of these events and the general public discontent it entailed resulted in the 2000 election win for the candidate for the Partido de Acción Nacional (PAN) Vicente Fox Quesada, the former president of Coca Cola Mexico, backed by public slogans such as “İQue se vayan!” (Get them out) – referring to the PRI. The 2000 elections were celebrated as a regime change from a one-party monopoly of political power to political pluralism and much progress was predicted in public opinion polls, because the main obstacle to this change– the hegemony of the PRI – had been removed. Signs were emerging that Mexico was on the right track to becoming a real democracy through a legitimately elected government. After only twelve years of PAN presidency, in 2012 Mexico again had a PRI president: Enrique Peña Nieto, elected with a 38.15% of the popular vote. The elections were followed by massive protests and questions concerning legality and corruption. Using the framework of clientelism, legitimacy and social choice, this thesis provides the means to answer the following research question: What are the underlying reasons for the PRI to have regained the presidency in Mexico in 2012, despite past legitimacy issues