Article Photos: Leftist candidate to challenge Mexico's election 2/3

  Andres Manuel Lopez Obrador, presidential candidate for the Democratic Revolution Party (PRD), attends a news conference in Mexico City, Thursday, July 12, 2012. Lopez Obrador says he will ask an electoral court to invalidate the results of the July 1 presidential election, charging there was vote buying and campaign overspending by the winner of official vote counts. (AP Photo/Eduardo Verdugo)