RIO DE JANEIRO – Brazilians vote Sunday in a razor-tight presidential runoff that has boiled down to a brutal, simple choice: four more years of Lula, or a Bolsonaro back in the seat of power – this time the son.

Sen. Flávio Bolsonaro, 45, the right-wing heir to his father's movement, rolls into election day as the man to beat after stunning Brazil's left with a first-round win on 4 October – a result President Trump instantly branded "very big."

Standing in his way is 80-year-old President Luiz Inácio Lula da Silva, chasing a fourth non-consecutive term and telling voters the country's democracy is what's really on the ballot.

It is Flávio Bolsonaro's election to lose – and he knows it.

'The time is almost here'

Bolsonaro's crowds came out roaring on the eve of the vote, flooding the streets of Rio de Janeiro's Barra da Tijuca – the neighborhood where his father, former President Jair Bolsonaro, keeps a home – dressed in the national yellow and green and promising a clean break from the Left.

"The time is almost here," Bolsonaro told supporters in a video posted to social media. "There are only a few hours left before we shape the future of our nation for the next 30 or 40 years."

He closed out the campaign in Belo Horizonte, capital of Minas Gerais – a must-win state for any presidential hopeful since the 1980s – and has pledged a hard crackdown on organized crime, alongside tax and public spending cuts.

He has also promised to free his father, who is serving a 27-year sentence for plotting a coup after losing the 2022 election, and is currently under house arrest because of ill health.

Voters in Rio didn't mince words about why they're with him.

"Brazil needs change, and Flávio is the person that represents that today, after so many years of the Left destroying the economy and the country," one supporter told the BBC.

Another said what sold her was his vow to "end violence in Brazil, end terrorism, narco-trafficking, and to reduce interest rates."

Historic comeback or bust for Lula

The numbers are unforgiving for the incumbent. Never in Brazil's modern electoral history has a candidate who trailed after the first round clawed back the deficit to win a runoff – the mountain Lula now has to climb.

His campaign's answer has been sheer volume: mass rallies across the country aimed at dragging back the 33 million Brazilians who simply didn't show up to vote earlier this month.

"It's true that the people want change, but they want to move forward. They don't want to go backward."

— President Luiz Inácio Lula da Silva

On Saturday, Lula took over Copacabana beach in Rio, telling a massive crowd the race had become a question of national "sovereignty" – and framing it as a contest between a man who kisses the Brazilian flag and one who kisses the American flag.

"We're going to win the election for one simple reason," he said. "It's true that the people want change, but they want to move forward. They don't want to go backward."

His supporters marched in Rio too, insisting the movement still has the muscle to turn the vote around.

"This movement is to show we have strength. We've woken up, we're coming to the street to make a difference and turn the vote around," a Lula backer named Roberta told the BBC.

One man in Brazil's national football shirt said Bolsonaro's side had "appropriated" the famous jersey – and that Lula's people were taking it back.

Trump in the crosshairs

Washington is all over this race, whether Brazil's left likes it or not.

Lula's administration has accused the United States of interfering in the election – an allegation the White House has dismissed as "baseless" – while Lula himself has insisted Brazil "does not fit into anyone's backyard," a swipe at what the Trump administration has dubbed the "Donroe Doctrine."

Bolsonaro is running the opposite playbook, arguing that partnering with Washington to smash the criminal gangs that run swaths of Brazilian territory is the only way to hand sovereignty back to the people living under them.

He has also branded Lula's Workers' Party as corrupt, hammering the sprawling financial scandals that dogged the party for years and turned millions of voters against it.

Lula and his party have answered by casting the election as a "battle for democracy," pointing to Jair Bolsonaro's coup-plotting conviction as proof that "Bolsonarismo" is a threat to the country's institutions.

What to watch Sunday night

Lula plans to watch the results come in from São Paulo, while Flávio Bolsonaro will be in the capital, Brasília – the same city where his father sits under house arrest.

For Brazil's right, it's the prize of a generation. For Lula, it may be the last stand.