Mexican President Enrique Peña Nieto "is taking an enormous political risk" by hosting Donald Trump in Mexico City on Wednesday, former President Vicente Fox said, decrying the Republican nominee's visit as "opportunistic" and a "political stunt" while apologizing on behalf of the country for the president's invitation."Trump is using Mexico, is using President Peña to push his sinking poll numbers," Fox said in an interview with CNN's "New Day" hours ahead of the scheduled meeting in the Mexican capital.