BRASILIA/RIO DE JANEIRO (Reuters) -- Brazil's presidential election is headed for a run-off vote, electoral authorities said on Sunday, after President Jair Bolsonaro's surprising strength in the first round spoiled rival Luiz Inacio Lula da Silva's hopes of winning outright.
With 99.7% of electronic votes counted, Lula was ahead with 48.4% of votes versus 43.3% for Bolsonaro, the national electoral authority reported. As neither got a majority of support, the race will go to a second-round vote on Oct. 30.
Several opinion surveys had shown the leftist Lula, who was president from 2003 to 2010, leading the far-right Bolsonaro by 10-15 percentage points ahead of Sunday's vote. The much tighter result dashed hopes of a quick resolution to a deeply polarized election in the world's fourth-largest democracy.
Bolsonaro had questioned polls that showed him losing to Lula in the first round, saying they did not capture enthusiasm he saw on the campaign trail. He has also attacked the integrity of Brazil's electronic voting system without evidence, and suggested he might not concede if he lost.
Political observers had said a wide margin of victory for Lula could sap Bolsonaro of support to challenge the electoral results. But Sunday's vote, extending a tense and violent election by another four weeks, revitalized his campaign.
"The extreme right is very strong across Brazil," said Carlos Melo, a political scientist at the Insper business school. "Lula's second-round victory is now less likely. Bolsonaro will arrive with a lot of strength for reelection."
Lula put an optimistic spin on the result, saying that it would only postpone his victory and that he looked forward to going head-to-head with Bolsonaro in a debate.
"We can compare the Brazil he has built to the one we built," he told reporters.
Bolsonaro was also calm and confident in his post-election remarks, disparaging polling firms for failing to gauge his support.
"I plan to make the right political alliances to win this election," he told journalists, pointing to significant advances his party made in Congress in Sunday's general election.
His right-wing allies won 19 of the 27 seats that were up from grabs in the Senate, and initial returns suggested a strong showing for his base in the lower house.
Outside Bolsonaro's family home in Rio de Janeiro's Barra da Tijuca neighborhood the mood was upbeat.
Maria Lourdes de Noronha, 63, said only fraud could prevent a Bolsonaro victory, adding that "we will not accept it" if he loses. "The polls in our country, the media, and journalists, are liars, rascals, shameless," she said.
Although Lula left the presidency 12 years ago with record popularity, he is now disliked by many Brazilians after he was convicted of accepting bribes and jailed during the last election. His conviction was later overturned by the Supreme Court, allowing him to run again for president this year, along with nine other candidates from an array of smaller parties.
A career lawmaker turned self-styled outsider, Bolsonaro rode a backlash against Lula's Workers Party to victory in 2018, uniting strands of Brazil's right, from evangelical Christians to farming interests and pro-gun advocates.
He has dismantled environmental and indigenous protections to the delight of commercial farmers and wildcat miners, while appealing to social conservatives with an anti-gay and anti-abortion agenda.
His popularity has suffered since the coronavirus pandemic, which he called a "little flu" before COVID-19 killed 686,000 Brazilians. Corruption scandals also forced ministers out of his government and focused a harsh spotlight on his lawmaker sons.
Yet Sunday's vote shows his support is far from collapsing.
Lula's proposals for Brazil have been light on details, but he promises to improve the fortunes of Brazil's poor and working classes, as he did as president from 2003-2010, when he lifted millions out of poverty and burnished Brazil's global influence.
While in power, Lula's approval rating soared as he expanded Brazil's social safety net amid a commodity-driven economic boom. But in the years after he left office, the economy collapsed, his hand-picked successor was impeached and many of his associates went to prison as part of a vast graft scandal.
Lula himself spent 19 months in jail for bribery convictions that were thrown out by the Supreme Court last year.