"Today, everyone says that my acceptance (among the people) is much greater than that of my opponent (ex-president Luiz Inacio Lula da Silva). But let's leave it to the polls ... let's leave this question with the electoral transparency commission," Bolsonaro said in an interview on SBT when asked if he would accept the result in the event of a defeat.

"If the transparency commission, in which the armed forces also participate, shows nothing abnormal, there is no reason to doubt the outcome of the elections," said the former army captain who has on several occasions and without proof raised the possibility of "fraud" at the electronic ballot box.

He had gone so far as to threaten not to recognize the results if he lost to his leftwing rival.

Lula was for months the big favorite in opinion polls, with a 21-point lead over Bolsonaro in May, according to the Datafolha institute.

But Bolsonaro surprised in the first round on October 2, winning 43 percent of the vote, only five points behind Lula, a much smaller gap than polls had predicted.

In the final stretch of the campaign, Bolsonaro has reduced his attacks on electronic voting and turned on polling firms, which he accused of "lying" to favor his main opponent.

The polls still put Lula in the lead, with 49 percent against 45 percent for Bolsonaro, according to Datafolha, with one percent undecided and four percent indicating they will cast blank votes.

Bolsonaro's interview replaced what should have been the second face-to-face debate between the two candidates, after Lula decided not to take part because of "incompatibility with his campaign agenda," according to the organizers.