Marina Silva, a popular environmentalist who finished third in the first-round of Brazil's presidential election, has endorsed the leading opposition candidate in the runoff with President Dilma Rousseff set for Oct. 26.

Aecio Neves surprised many analysts by finishing ahead of Silva in the initial vote on Oct. 5 and his campaign said Silva's endorsement would be key to their effort to beat Rousseff's bid for a second term.

Silva announced Sunday that she would support Neves and trusted that he would fulfill the proposals he has promised for Brazil.