Luiz Inácio Lula da Silva, the Brazilian president, has staged a dramatic election fightback, defeating his far-right opponent, Flávio Bolsonaro, to claim a historic fourth term in power.

With nearly 99% of votes counted the 80-year-old leftist received 51.75% of the vote to his 45-year-old rival’s 48.25%.

Lula narrowly lost the first round of the election to Bolsonaro in early October, casting his political future into doubt and plunging progressive Brazilians into three weeks of despair. Never, since the return of democracy in the 1980s, has the first round runner-up won the second vote.

But Lula did precisely that on Sunday, prompting joyous scenes on the streets of São Paulo, where he had been following the count, and at the hotel where he was watching the count.

As the result was confirmed, Reginaldo Lopes, a key Lula ally, told the Guardian: “I feel incredible … This is Brazil telling the world that the extreme right is fascist, that the extreme right is against black people, is against the poor, against the state, against gay people … We are going to reorganize the democratic forces [in this country.”

The incumbent, who had lost by 2.2 million votes three weeks ago, has now won by 4.3 million.

The 81-year-old leftist appears to have made up much of the difference through what his allies had identified as his main opportunity: persuading his voters to turn out. After a record abstention rate of 21.08% in the first round, which disproportionately affected Lula voters because they tend to live farther from polling stations, the rate fell to 19.21%.

For Lula, who turns 81 on Tuesday, the victory represents a sensational final chapter in a storied political career that began when he emerged as a union leader in São Paulo’s industrial suburbs in the late 1970s.

After entering politics, the former factory worker who was born in rural poverty made three unsuccessful presidential bids, in 1989, 1994 and 1998, before finally becoming Brazil’s first elected working-class president in 2002.

Lula stepped down after the maximum two consecutive terms allowed by the constitution but returned to power after winning the 2022 election against Bolsonaro’s father, then the incumbent president Jair Bolsonaro, who was subsequently jailed for plotting a coup.

Lula’s win is bad news for Bolsonaro who is serving a 27-year sentence for that botched power grab and was hoping to be freed and given a role in government had his son prevailed.

It is also a blow for Donald Trump, the Bolsonaro clan’s most important international ally. The US president had been hoping Bolsonaro would become the latest in a series of pro-Trump leaders to take power in Latin America, including Abelardo de la Espriella in Colombia, Daniel Noboa in Ecuador, José Antonio Kast in Chile and Javier Milei in Argentina.

Confirmation of Lula’s victory was greeted with anger and bewilderment in Brasília, where Bolsonaro is living under house arrest and where his son watched the count.

Lula’s victory came after his supporters staged two massive shows of support on Saturday, with more than a million people flocking to Rio’s Copacabana beach and an even larger number marching on Paulista Avenue at the heart of São Paulo.

Speaking at the Rio rally, truck driver Josias Silva said he said he was confident of a Lula comeback, after weeks of student-led anti-Bolsonaro protests.

“The people have woken up … There’s never been a demonstration like this one. This is the biggest protest in the history of Brazil. And we are going to win tomorrow with more than 60% of the votes,” Silva claimed.

Hundreds of Lula supporters returned to Paulista Avenue on Sunday evening to watch the vote count, waving red flags stamped with the face of the president.

“I feel so very happy being here, and being here fighting for Lula,” said Camilo Buarque, 35, as he watched Lula take an early lead. “My confidence comes from the energy and the happiness and the love of these people [around me]. This is democracy.”

“My heart is beating a thousand beats a second but I’m confident,” said Ester Almeida, 28, another Lula supporter who was at the rally.

Many people on the streets of São Paulo were angry at an apparent attempt by pro-Bolsonaro politicians to derail the election by sabotaging public transport in Lula-leaning voting areas across the country.

“I think it’s another coup attempt that the extreme right is trying in Brazil. But we need to really fight so we can win,” said Lucas Lopes, a 32-year-old from São Paulo who works with public relations.

But that alleged attempt to scupper a Lula victory failed.

“I’ll be sincere: in the first round the left failed. But in the second round they woke up,” said Caio Marques, a 40-year-old photographer from Franca, a city in the interior of São Paulo state. “And there is no coup that will take this away from us.”