Mexican leftist presidential candidate Andres Manuel Lopez Obrador said Monday he will mount court challenges against the results of the July 1 election, claiming vote-buying and campaign overspending by the winner of official vote counts, Enrique Pena Nieto. The announcement comes amid rising calls to investigate what appears to have been the distribution of thousands of pre-paid gift cards to voters before the election, and allegations by Lopez Obrador’s supporters that some state government officials passed funds to Pena Nieto’s campaign effort. Lopez Obrador finished about 6.6 percentage points behind Pena Nieto of the old guard Institutional Revolutionary Party, or PRI.