Brazilian Green party presidential candi

Brazilian Green party presidential candidate Marina Silva, a former environment minister, speaks during an individual debate at the XIII National Meeting of Mayors, in Brasilia, on May 19, 2010. Chief minister Dilma Rousseff -- Brazilian President Luiz Inacio Lula da Silva's pick to be his successor when he stands down at the end of this year -- has become a frontrunner in the election race, pipping the previous favorite, former Sao Paulo state governor Jose Serra for the first time, a survey showed Monday. Brazil's presidential election will be held October 3, with a run-off between the top two candidates on October 31 if one does not get more than half of the vote. AFP PHOTO/Evaristo SA (Photo credit should read EVARISTO SA/AFP via Getty Images)