Marina Silva, the former environment minister who shot to the top of the polls after entering Brazil's presidential contest less than three weeks ago, lost a senior campaign aide on Tuesday over her opposition to same-sex marriage.

The controversy arose with the inclusion of support for same-sex marriage in the platform that Silva and her party, the PSB, presented last Friday.

Silva, a fervent evangelical Christian, reversed course on Saturday by saying that the platform referred only to civil unions between people of the same sex.

"We were surprised" with the change, the heretofore coordinator of gay issues for Silva's campaign, Luciano Freitas, a well-known activist, said going on to confirm that he had resigned.

Freitas' resignation follows that of PSB general secretary Carlos Siqueira, who abandoned the campaign after other disagreements with Silva, who was named the party's candidate 20 days ago following the death in a plane crash of the party's original nominee, Eduardo Campos.

Silva explained the change in the election platform as the "correction of a mistake."

"Marriage is for people of different sexes," she said.

Civil unions were made legal in Brazil by a 2013 decision of the National Council of Justice, but Congress has not passed any law on marriage.

Whether by coincidence or not, the change followed protests by leaders of Brazil's burgeoning Pentecostal churches, who accused Silva of having "mocked" the principles of the faith.

Brazil, a nation of more than 202 million people, has an estimated 20 million evangelicals and a roughly equal number of gays and lesbians.

Polls indicate that none of the seven candidates will gain the majority needed for outright victory in the Oct. 5 election, thus necessitating a second round of voting on Oct. 26.

Before Silva joined the contest, the runoff was expected to pit incumbent Dilma Rousseff against then-main challenger Aecio Neves and to result in a second four-year term for the current head of state.

Silva, however, has relegated Neves to a distant third and surveys show her beating Rousseff in a runoff.

The gay-marriage controversy within Silva's campaign was taken advantage of on Monday by Rousseff after the second presidential debate concluded.

"I don't think that proposals should be changed, above all when one speaks of rights and even moreso if it deals with homophobia, which is an insult for Brazil," said Rousseff after an exchange that revolved around economic matters.

Silva, an Afro-Brazilian, served as environment minister for part of the 2003-2011 Workers Party government of President Luiz Inacio Lula da Silva, Rousseff's political mentor. She finished third in the 2010 presidential election as leader of the Green Party. EFE