Leftist presidential candidate Andres Manuel Lopez Obrador and his party formally filed a petition with Mexico's electoral court Thursday to overturn the election results. They claim there was vote buying and campaign overspending by Enrique Pena Nieto, who was named the election's official winner with just over 38 percent of votes..
Lopez and his party turned in the petition along with at least 20 boxes containing alleged proof of vote-buying by members of Nieto's party, Institutional Revolutionary Party, also known as PRI.
The court has until early September to deal with any challenges and determine whether to validate the presidential election.
The Associated Press contributed to this report.