Brazil's far-right presidential candidate Jair Bolsonaro has widened his lead over leftist Fernando Haddad ahead of Sunday's deeply polarized election, and would win a likely second-round run-off later this month, a CNT/MDA poll showed on Saturday.

With more polls due later on Saturday, the CNT/MDA survey captured a palpable surge in Bolsonaro's support in recent days that could, if it continues, see him win a majority of votes on Sunday, and avoid the Oct. 28 run-off.

Bolsonaro's support grew to 36.7 percent from 28.2 percent in the previous late-September poll, while his main rival, second-placed Workers Party candidate Haddad, slipped to 24.0 percent from 25.2 percent.

But perhaps more tellingly, Bolsonaro's share of valid votes shot up to 42.6 percent from 35.3 percent, putting him tantalizingly close to Brazil's first initial-round electoral victory since 1998. Haddad's share of valid votes fell from 31.5 percent to 27.8 percent.

Bolsonaro, who has surged on widespread anger over rising crime, a drifting economy and the prospect of the divisive Workers Party returning to power, was also seen beating all his possible rivals in the second-round run-off.

The 63-year-old former army captain, who is still recovering from a serious stab wound received during the campaign, enjoys passionate support thanks to grassroots organizing on social media, but terrifies critics who label him a "Tropical Hitler."

He vows to loosen gun laws so citizens can defend themselves, protect family values and slug it out with powerful drug gangs responsible for a record 64,000 murders in 2017.

On Friday, Bolsonaro appealed to Brazilians to vote for him in a live Facebook feed from his Rio de Janeiro home, asking them to give him a majority to avoid a second vote.

Haddad's support relies on the popularity of his mentor, jailed former president Luiz Inacio Lula da Silva, who was barred from running due to a corruption conviction.

Haddad on Saturday campaigned in the northeastern state of Bahia, Lula's political heartland, where the 55-year-old recorded a video message alongside the state's Workers Party Governor Rui Costa, urging his supporters to be wary of the political messages they receive via social media.

"A lot of lies on the internet," he said. "The other side is a bit desperate, because they think that if Bolsonaro is forced to debate, he will melt. So they want Bolsonaro to win without having to debate, which is bad for democracy."

About 26 percent of voters say they have yet to decide who to vote for, according to a Datafolha poll released on Thursday.

"We will accept the result whatever it is, there should be no doubt of that," Bolsonaro said on Friday, in a bid to calm fears he would call for a military coup if he lost.

Bolsonaro, who is backed by a group of retired generals, said last week he would only accept victory.

A Bolsonaro government would speed up the privatization of state companies to reduce Brazil's budget deficit and relax environmental controls for farming and mining. It would also block efforts to legalize abortion, drugs and gay marriage.

In an interview published on Friday by the newspaper Estado de Sao Paulo, one of the candidate's top economic advisers said Bolsonaro would push ahead with privatizing state power firm Centrais Eletricas Brasileiras SA, or Eletrobras.

However, former army General Oswaldo de Jesus Ferreira pledged to keep state oil giant Petroleo Brasileiro SA, known as Petrobras, in government hands.

Hydroelectric dam projects on the Tapajos river in the Amazon basin that were stopped due to environmental concerns would be discussed again, Ferreira said.

But he said the expansion of soy, corn and sugar cane plantations would not be allowed in the Amazon region, where environmentalists say deforestation is on the rise again.