Enrique Pena Nieto, presidential candidate of the Institutional Revolutionary Party (PRI), waves after exit polls showed him in first place, in Mexico City July 1, 2012. The party that ruled Mexico for most of the 20th century claimed victory in a presidential election on Sunday as a senior election official said the party’s candidate, Enrique Pena Nieto, held an irreversible lead over his rivals. REUTERS/Tomas Bravo (MEXICO – Tags: POLITICS ELECTIONS POLITICS)