A marine stands guard in downtown Veracruz November 26, 2012. For Enrique Pena Nieto, who takes office on Saturday as Mexico's new president, the fight against crime and criminal organizations will be the biggest challenge of his government. The cover of the magazine shows a photograph of Mexico's outgoing President Felipe Calderon and the headline reading "The nightmare is over." Picture taken November 26, 2012 REUTERS/Edgard Garrido (MEXICO - Tags: POLITICS MILITARY)