Heraldo de Madrid - Lula, Bolsonaro in final debate showdown before Brazil vote

The son of former far-right president Jair Bolsonaro took a shock lead over Lula in a first-round vote, setting up a runoff on Sunday that could see Latin America's largest country join a regional shift to the right championed by US President Donald Trump.

The senator's surprise lead kicked the Brazilian left into action with massive rallies and an energetic online campaign to try to deliver Lula, 80, a comeback.

Both sides have accused each other of social media abuses and Meta, the parent company of Facebook, Instagram and WhatsApp, is under fire over alleged unequal treatment of the candidates.

A Datafolha institute survey published Thursday evening shows the pair tied with 50 percent of voting intentions each, compared to Bolsonaro's four-point lead in polls published two weeks ago.

"Lula is on an upward trajectory, but he has not yet landed a decisive blow to turn the tide. This debate could be his last chance," political analyst Leandro Gabiati, director of the consulting firm Dominium, told AFP.

The first debate on Sunday quickly deteriorated into a barrage of insults, leaving little room for concrete proposals, and voters more confused than ever.

A Quaest poll after the debate showed the number of undecided voters had doubled from seven to 14 percent.

"The debates have once again descended to a fifth-grade level, which is absurd," said dentist Lizie Moreira, telling AFP she plans to vote for Bolsonaro.

- 'Fake news' -

An online petition with over a million signatures has asked the Globo TV network to implement a live fact-checking system during the debate.

The candidates have accused each other of spreading disinformation during a campaign heavily based on fearmongering.

At a rally in the northeastern city of Fortaleza on Wednesday, Flavio Bolsonaro said he had to "debunk a lot of fake news," particularly claims that he would end social welfare programs as a way to cut spending.

He has promised to get tough on crime, creating 500,000 more spots in prisons and slash government spending.

"Change doesn't mean depriving people of their rights," Lula has said.

Lula "represents everything that I am," said 22-year-old Gabriela Ferreira at a leftist demonstration in the southeastern city of Belo Horizonte.

"I am poor. I am a student. I depend on a scholarship to do my degree."

The former union leader presents himself as a defender of democracy, and is largely counting on opposition to the Bolsonaro family's return to power.

Jair Bolsonaro is serving a 27-year sentence for attempting a coup after his electoral defeat to Lula in 2022.

- Legal battles -

The campaign has also seen a flurry of legal challenges and court rulings.

Both candidates went to court this week to demand their opponent be disqualified over abuse of social media.

Lula's campaign has accused US tech Meta of "interference" in favor of Flavio Bolsonaro via alleged "algorithmic manipulation."

Meta has denied taking any actions to favor one side in the election, but admitted that some of Lula's campaign ads had been mistakenly deactivated due to technical errors.

An electoral court on Thursday gave Meta and X 24 hours to explain their criteria for distributing political content and adverts, as well as how they employ artificial intelligence.

Lula on Thursday called for the defeat of Meta's "digital empire" during a live broadcast with the "Lula's Army" WhatsApp channel -- which has over eight million followers.

"Meta will have to be reinvented; it cannot simply assume it can go on deceiving humanity forever."

Lula's team is concerned about "the obvious alignment between Meta and the US government," Joao Brant, his campaign's digital strategy advisor, told AFP.

Bolsonaro meanwhile accuses Lula of "abuse of power" for the alleged mass dissemination of government actions during the electoral period through an official WhatsApp account.

Z.Quintana--HdM