Brazil will vote in a polarizing presidential election on Sunday, with all eyes on whether leader Luiz Inacio Lula da Silva can win in a single round – and whether incumbent Jair Bolsonaro will accept the result.

The campaign, which left the Latin American giant deeply divided, ended with former President Lula (2003-2010) leading ex-army captain Bolsonaro with 50 percent of the valid vote to 36 percent, according to a final Datafolha Institute poll released Saturday night .

The numbers put Lula at the top of the score required to win outright and avoid an Oct. 30 runoff: half the valid votes plus one.

But Bolsonaro, known for his combative style, has repeatedly said “only God” could remove him from office, has attacked alleged fraud in Brazil’s electronic voting system and has vowed his re-election bid can only have three outcomes: “prison, death.” or victory.”

Lula, the charismatic but ailing ex-president who is targeting a comeback at 76, says he fears the incumbent will cause “uproar” if he loses – a worry often heard in Brazil ahead of Election Day.

Bolsonaro’s attacks on the electoral system have sparked fears of a Brazilian version of the riots that broke out in the US Capitol last year after his political idol, former President Donald Trump, refused to accept his electoral defeat.

“I think (Bolsonaro) will contest the election result if he loses,” said political scientist Adriano Laureno of the Prospectiva consultancy.

“But that doesn’t mean he’ll succeed. The international community will quickly see the outcome… There may be some kind of turmoil and uncertainty surrounding the transition, but there is no risk of democratic rupture.”

Observers from the Organization of American States, the Carter Center, the Inter-American Union of Electoral Organizations (UNIORE) and other international bodies will observe the vote.

The White House, meanwhile, said the United States would be “closely monitoring” the vote.

More than 500,000 security forces will be deployed on election day.

Public Safety Secretary Anderson Torres tried to downplay fears of unrest.

“We have a choice, not a war,” he said.

Lula, the former metalworker-turned-penny-to-be-the most popular president in Brazilian history, is attempting to stage a remarkable return four years after he fell spectacularly from grace when he was jailed for 18 months on controversial corruption charges.

Lula has been charged under a massive bribery scheme centered on state oil company Petrobras and won the right to run for office last year when the Supreme Court overturned his convictions, ruling that the lead judge in the case was biased .

Meanwhile, 67-year-old Bolsonaro, who swept into office in 2018 on a wave of anti-establishment outrage, has lost his outsider glamor.

The president vows to defend “God, country and family” and retains the relentless support of his “Bibles, Bullets and Beef” base – evangelical Christians, security hardliners and the powerful agribusiness sector.

But he has lost moderate voters with his management of a sluggish economy, his savage attacks on Congress, the courts and the press, a wave of destruction in the Amazon rainforest and his failure to stem the devastation of Covid-19, which has been claimed more than 685,000 live in Brazil.

Many voters are deeply disillusioned with both contenders – and the lack of other options – in a race in which none of the other nine candidates managed to break out of single digits in the polls.

“It’s like we have a gun to our heads,” 27-year-old Uber driver Matheus Fernandes told AFP in Lula’s home state of Pernambuco.

His plan: hand in a blank ballot.

Lula plans to vote in Sao Bernardo do Campo, outside of Sao Paulo, where he rose to prominence as a union leader. Bolsonaro, a former Rio de Janeiro congressman, will vote in the famous beach town and then return to Brasilia to see the results.

Polling stations open at 8am and close at 5pm (1100-2000 GMT), with results expected around two hours later.

Brazil’s 156 million voters will also elect the lower house of Congress, a third of the Senate and governors and state representatives in all 27 states.