Mexican voters will head to the polls on Sunday, with the bitterly contested race to replace President Vicente Fox in a dead heat. Andres Manuel Lopez Obrador, the former mayor of Mexico City and Felipe Calderon, once Fox's energy minister, are virtually tied, the most recent polls suggest. It will be just the second democratically held national election since the country's transition from a one-party state. The Institutional Revolutionary Party, under a succession of names, governed the country from 1929 until Fox was elected in 2000. Its candidate, Roberto Madrazo, is currently third in the polls. Both Obrador and Calderon...