Mexico’s electoral board has confirmed the victory of PRI candidate Enrique Peña Nieto in last week’s presidential vote. Peña Nieto belongs to the Institutional Revolutionary Party, or PRI, the party that ruled Mexico from 1929 to 2000. His chief rival, the leftist Andrés Manuel López Obrador, has accused the PRI of electoral fraud and has vowed to challenge the results in court. On Saturday, tens of thousands of people marched in Mexico City to protest the election results and demand a government probe.