The election will decide if the country returns a leftist to the helm of the world’s fourth-largest democracy or keeps the far-right incumbent in office.

With 98.8% of the votes tallied in Sunday’s election, former president Luiz Inacio Lula da Silva had 48.1% support and incumbent president Jair Bolsonaro had 43.5% support.

The outcome was a much closer result than opinion polls had suggested.

Supporters of former President of Brazil and Candidate for the Worker's Party (PT) Luiz Inacio Lula da Silva wait for him at the end of the general election day at Paulista avenue on October 2, 2022 in Sao Paulo, Brazil. (Photo by Mauro Horita/Getty Images)

Brazil’s election authority said the result made a second-round vote between the two candidates a mathematical certainty.

Nine other candidates were also competing, but their support pales to that for Mr Bolsonaro and Mr da Silva.

The tightness of the result came as a surprise, since pre-election polls had given Mr da Silva a commanding lead.

The last Datafolha survey published on Saturday found a 50% to 36% advantage for Mr da Silva among those who intended to vote. It interviewed 12,800 people, with a margin of error of two percentage points.

“This tight difference between Lula and Bolsonaro wasn’t predicted,” said Nara Pavao, who teaches political science at the Federal University of Pernambuco.

Carlos Melo, a political science professor at Insper University in Sao Paulo, said: “It is too soon to go too deep, but this election shows Bolsonaro’s victory in 2018 was not a hiccup.”

Mr Bolsonaro outperformed in Brazil’s southeast region, which includes populous Sao Paulo, Rio de Janeiro and Minas Gerais states, according to Rafael Cortez, who oversees political risk at consultancy Tendencias Consultoria.

“The polls didn’t capture that growth,” Mr Cortez said.

Mr Bolsonaro’s administration has been marked by incendiary speech, his testing of democratic institutions, his widely criticised handling of the Covid-19 pandemic and the worst deforestation in the Amazon rainforest in 15 years.

But he has built a devoted base by defending conservative values and presenting himself as protecting the nation from leftist policies that he says infringe on personal liberties and produce economic turmoil.

Mr Da Silva is credited with building an extensive social welfare programme during his 2003-2010 tenure that helped lift tens of millions into the middle class.

He is also remembered for his administration’s involvement in vast corruption scandals and his own convictions, which were later annulled by the Supreme Court.

Mr Da Silva is credited with building an extensive social welfare programme during his 2003-2010 tenure that helped lift tens of millions into the middle class.

He is also remembered for his administration’s involvement in vast corruption scandals and his own convictions, which were later annulled by the Supreme Court.

Polls closed at 5pm on Sunday nationwide and because the vote is conducted electronically, initial results are out quickly. Final results are usually available a few hours later.

More than 150 million Brazilians were eligible to vote, though abstention rates can reach as high as 20%.

The election wound up being far tighter than anticipated, both in the presidential contest and those for governorships and congressional seats.

Voters now have four weeks to decide which of the two should lead Brazil.

Brazil election: Lula and Bolsonaro to face run-off as neither candidate receives 50 per cent support