Brazilian presidential hopeful Aecio Neves on Sunday earned a key endorsement in his bid to defeat incumbent Dilma Rousseff — from environmentalist candidate Marina Silva.

The Social Democrat Neves lost to Rousseff in the first round a week ago, but opinion polls now show him in a statistical dead heat with her ahead of the October 26 run-off — making Silva’s backing vital.

Aecio Neves with his wife, Leticia weber after the election

Dilma Rousseff: polls deadlock with Neves

The pair are battling to run Latin America’s largest country of 202 million, which is also the world’s seventh-largest economy.

“Taking into account the policy commitments made by Aecio Neves, I declare my support. I vote for Aecio Neves,” said Silva, whose once promising campaign flamed out in the first round.

Silva said the pro-business Neves had moved sufficiently close to her positions on several issues to warrant her endorsement.

“I see a swathe of historic commitments,” said Silva, citing his promise to maintain social welfare programs that have lifted tens of millions of Brazilians out of poverty over the past decade.

Silva’s campaign promise of a “new politics” saw her garner 22 million votes in the first round — which Neves must court if he is to win.

Neves, the 54-year-old scion of a political dynasty and business-world favorite, must persuade at least six in 10 Silva voters to back him if he is to make up an eight-point first round gap on Rousseff,

The incumbent — Brazil’s first woman president and a former leftist guerrilla once imprisoned and tortured by the country’s military regime — is bidding to hand her Workers Party (PT) a fourth straight term.

Latest polls show Neves just leading Rousseff by 46 percent to 44 percent — well within the margin for error.

Silva, who ran on the Socialist Party (PSB) ticket after initial pick Eduardo Campos died in an August plane crash, made Neves wait before offering her personal support.

He has already obtained endorsements from both her party and the Greens