A leading candidate for governor of a Mexican state has been gunned down in an ambush while campaigning in the northern state of Tamau-lipas.<br /><br />Felipe Calderon, the Mexican president, blamed drug gangs for Monday's killing of Rodolfo Torre, saying it was evidence that gangs were trying to infiltrate the election process.<br /><br />Some 25,000 people have been killed since Calderon came into office in 2006 and launched a crackdown on drug gangs and related violence.<br /><br />Al Jazeera's Mariana Sanchez reports from the town of Nuevo Laredo in Tamau-lipas. (June 29, 2010)
