Tens of thousands of supporters of Brazil’s leftwing president, Luiz Inácio Lula da Silva, have streamed on to Rio’s most famous beach for a giant protest they hope will propel him towards a historic election fightback against his far-right rival, Flávio Bolsonaro.

Nearly 159m Brazilians will vote in the election’s runoff on Sunday, with the pair tied in the polls after Bolsonaro won the first round on 4 October by 47% to 45%.

On Saturday, under a fierce sun, red-clad crowds packed the 2.5-mile Copacabana beach in an attempt to help Lula clinch a dramatic and unprecedented comeback. Never since the return of democracy to Brazil in the 1980s has the first-round loser managed to bounce back.

Josias Silva, a 61-year-old truck driver, voiced confidence that his 80-year-old president would win a fourth non-consecutive term. He carried a homemade sign to the carnival-like procession reading: “Lula re-elected. Tomorrow will be a new day.”

“The people have woken up,” Silva said of the large pro-Lula street protests that have swept Brazil since the leftist’s first-round defeat, many led by students.

“Young people know we need this victory because otherwise we will have dictatorship again – and we don’t want dictatorship. We don’t want hatred. We don’t want guns. We want a country of love,” added Silva, celebrating the large number of people who came to witness one of the final presidential campaign rallies in Lula’s storied 50-year political career.

“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.

Polls suggest a far tighter margin and most analysts see Bolsonaro, whose father, Jair Bolsonaro, was president from 2019 to 2022, as the slight favourite, having sold himself to voters as someone who will tackle chronic levels of violent crime with an iron fist.

However, in recent days Lula has appeared to regain the initiative and climb in the polls, amid a succession of scandals involving his rightwing foe. Last week the Brazilian magazine Piauí claimed that at the height of Brazil’s 2020 coronavirus outbreak, Flávio Bolsonaro attended a boat party attended by sex workers and vaccine lobbyists hoping to strike a deal with the government of his father.

Some experts speculate a Lula comeback may be possible. At the Copacabana rally, activists unfurled an enormous yellow and green banner declaring: “WE ARE GOING TO TURN THIS AROUND!”

“I’m super excited. Lula’s going to win,” said Marta Moraes, a 59-year-old restaurateur, as she joined Saturday’s demo.

Moraes said the election was not about left versus right. “We’ve nothing against the right … what we’re against is Bolsonarismo,” she said, tears filling her eyes as she recalled how Flávio Bolsonaro’s father botched the response to Covid during his chaotic 2019-2022 administration.

“I lost four members of my family because of Bolsonaro’s neglect,” Moraes said.

Jair Bolsonaro is serving a 27-year prison sentence for plotting a coup after he lost the 2022 election to Lula. Many Brazilian democrats fear he will be released – and could even return to government – if his son wins. Reports in the Brazilian press suggest several of Bolsonaro’s fellow plotters – who are now in prison or hiding in exile – may be given top military and police jobs in a Bolsonaro administration.

Cammy Marinho, a 49-year-old DJ and activist, said: “I’m here to prevent democracy becoming extinct – which is what the Bolsonaro family wants”.

Marinho said she had spent the past fortnight fighting to persuade people who voted for Bolsonaro, or did not vote in the first round, to back Lula.

“It’s non-stop work: in the bakery, in the supermarket, on the underground – whenever you feel there is an opening to talk to someone and show to them the reality, everything that Lula has done and is doing for the people and everything that this [Bolsonaro] family has done against the people,” she said.

Many marchers were part of the so-called “Lula’s Army” – a 10 million-member WhatsApp group that was created after the first round in the hope of turning the election around.

“Being a soldier in Lula’s army … means fighting for Brazilian democracy. This isn’t a normal election,” said Isabella Gaze, 64, a retired teacher and one of the group’s members.

“They constantly claim Lula is corrupt. But the truth is that they represent the most rotten and worst part of Brazilian politics. This is what we are fighting against now,” Gaze said of the Bolsonaros.

Many of the faces on Copacabana beach were teenagers, including 14-year-old Heitor Lopes da Silva. Silva had come from the city of Duque de Caxias in his wheelchair, with a placard that said: “Lula, I’m a person with a disability and I’m here to support you.”

“My whole life I’ve believed Lula was a good president. [Bolsonaro] represents the destruction of Brazil …. he represents sadness and death,” he said of the Bolsonaro-era Covid catastrophe.

Large crowds of Bolsonaro supporters also hit the streets, including in Belo Horizonte, the capital of Minas Gerais state, which has Brazil’s second-largest electorate after São Paulo, and is a key bellwether. No presidential candidate has ever won the presidency without securing Minas Gerais, where Bolsonaro led by just under 5% in the first round.

Thousands of Bolsonaristas gathered to see their candidate in a palm-lined plaza called Praça da Liberdade. To the booming sound of AI-generated funk carioca tracks praising Bolsonaro, a sea of supporters dressed in Brazil’s yellow football jersey waved Brazilian flags – and many of the United States too.

“The US is a great nation. Who wouldn’t want to be aligned with them?” said 56-year-old cosmetics entrepreneur Marcos Antonio, holding a flag that merged the emblems of both countries.

“I don’t want an alliance with Cuba or Venezuela. I want to move forward,” Antonio added. When reminded that Venezuela was currently aligned with the US after Donald Trump’s January invasion, he said: “True. But for now, a fully right-wing government hasn’t been installed yet. It’s in transition.”

Antonio Carlos Costa Jr, the 59-year-old owner of a shooting club, complained: “Lula did nothing for the country.”

Jair Bolsonaro relaxed gun ownership and buying laws – which security experts agree ended up diverting many firearms to criminal gangs – whereas Lula tightened regulations once again. “Jair Bolsonaro simply gave citizens the right to defend themselves, and his son will do the same,” said Costa Jr.

Lula supporters scoff at the idea that Bolsonaro, who has a history of well-documented ties with members of Rio’s paramilitary “militia” groups, could rid Brazil of criminality.

“If we vote the militias into power, we will be living in a dictatorship,” said Erika Cavalcante, 43, an architect who came to the march with a sign reading: “Don’t let the mobsters win.”