Brazilian President Luiz Inacio Lula da Silva will clash with his right-wing challenger Flavio Bolsonaro in a second and final televised debate on Friday, as both make a last-ditch effort to sway undecided voters.
The son of former far-right president Jair Bolsonaro beat Lula by two percentage points in the first round of presidential elections earlier this month, nabbing 47 percent of the vote.
The senator's surprise lead has kicked the Brazilian left into action, with enormous rallies staged across the country ahead of Sunday's runoff.
The incumbent, on the cusp of 81, has meanwhile upped his social media game at the eleventh hour, posting selfie-mode videos and even buying his first-ever cell phone.
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.
Brazilians are holding their breath ahead of the Friday night program hosted by the country's largest network, TV Globo, in Rio de Janeiro.
The first debate on Sunday quickly lapsed into a barrage of insults, and left little room for concrete proposals.
"The debates have once again descended to a fifth-grade level, which is absurd," dentist Lizie Moreira told AFP in Rio.
The 60-year-old will vote for Bolsonaro and considers Lula's policies "populism."
'Fake news'
An online petition with over a million signatures has asked Globo to implement a live fact-checking system for claims made by both candidates during the debate.
Each side has accused the other of spreading massive amounts of disinformation during the campaign.
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 also promotes the hardline security rhetoric of other right-wing leaders across Latin America, promising to lower the cost of living and saying he wants Lula to "retire."
"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 election is playing out over rallies, televised debates, and to a huge extent social media, but the courts are also proving instrumental in the fight.
Both candidates went to Brazil's top electoral court this week to demand their opponent be disqualified, each time alleging abuse of social media.
Pressure is being piled on Meta, the parent company of Facebook, Instagram and WhatsApp.
Lula's campaign accuses the US tech giant of election "interference" in favor of Flavio Bolsonaro via alleged "algorithmic manipulation."
Meta has denied taking any actions to favor one side in the election, but previously said that some of Lula's campaign ads had been mistakenly deactivated due to technical errors.
The company's independent oversight board issued criticisms this week that bolstered the Brazilian left's complaints, as did United Nations experts.
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.
US President Donald Trump, an ally of Jair Bolsonaro, meanwhile is watching the rise of the political right across Latin America with glee.