Bolsonaro, the 67-year-old president known for his gloves-off style, led one of his trademark motorcycle rallies from the north side of Sao Paulo to the city's Ibirapuera park, grinning and waving at the head of a battalion of bikers decked out in black leather and the yellow and green of the flag.
About five kilometers (three miles) from there, Lula, the 76-year-old ex-president who led Brazil from 2003 to 2010, held his own rally on the economic capital's main avenue, Avenida Paulista, gathering a sea of red-clad supporters waving banners ranging from "Lula 2022" to the rainbow-colored LGBTQ pride flag.
With the country deeply divided, tension is running high heading into Sunday's election which Lula is gunning to win outright, without the need for a runoff on October 30.
A poll from the Datafolha institute released Thursday put the charismatic but tarnished leftist on the cusp of a first-round win, with 50 percent of valid votes, to 36 percent for Bolsonaro.
To win outright, he would need 50 percent plus one vote.
The poll's margin of error was plus or minus two percentage points.
Bolsonaro has repeatedly signalled he could challenge an election loss, saying "only God" can remove him from office and alleging, without evidence, rampant fraud in Brazil's electronic voting system.
"We're going to win in the first round -- 64 percent of the vote," Bolsonaro's congressman son Eduardo said at the rally in Sao Paulo, alleging, like his father, that polls showing Lula ahead are fake.
Lula said Friday he feared the incumbent would create "turmoil" if he lost.
Some fear a possibile Brazilian version of the unrest that rocked the United States last year after Bolsonaro's political role model, former president Donald Trump, refused to accept electoral defeat.
"You always have to brace for trouble with Bolsonaro -- he's capable of anything," 52-year-old retiree Anderson Momesso told AFP at the Lula rally.
But 29-year-old teacher Ully Kotler said she was confident the "complete tragedy" of Bolsonaro's government had left him so isolated that "all he can do is stomp his feet and threaten a coup -- it won't go much beyond that."
Bolsonaro's popularity has been dented by his chaotic management of Covid-19 and the economy.
Security has been tight around both candidates, who rarely campaign without bullet-proof vests, after Bolsonaro was stabbed at a rally during his successful 2018 electoral race.
The final hours of the campaign, which closes at midnight, "will be very tense -- all eyes will be on the slightest detail that could tip the balance one way or the other," said political scientist Jairo Nicolau of the Getulio Vargas Foundation.
The homestretch already descended into mud-slinging Thursday when Lula and Bolsonaro traded insults in their final presidential debate.
Bolsonaro wasted no time pouncing on the controversial corruption charges that have long dogged Lula. The Supreme Court threw out his conviction last year, ruling the judge who jailed him was biased.
"You liar, ex-inmate, traitor," Bolsonaro spat at Lula on Thursday.
Lula, a former metalworker who rose from destitute poverty to become the most popular president in Brazilian history, responded in kind.
"It's ugly for the president of the republic to blatantly lie all the time... That's why the people are going to send you packing," he said in his trademark gravelly voice.
The incumbent received an endorsement Saturday from Hungary's rightwing Prime Minister Viktor Orban, who said: "I have met many leaders but not many as exceptional as your President Bolsonaro," in a video posted on Bolsonaro's Twitter account.
Two final opinion polls are due to be released Saturday evening, from Datafolha and fellow polling institute Ipec.