Twenty-one days and an "army" of voters.
That is all it took for a social media movement to grow so vocal it flipped the Brazilian election on its head and delivered Luiz Inácio Lula da Silva an unexpected historic fourth presidential term.
The 81-year-old, known colloquially as Lula, surged to an extraordinary triumph on Sunday by overcoming Flávio Bolsonaro, the son of former far-right president Jair Bolsonaro.
A WhatsApp group appeared to be a key factor in Lula's re-election amid claims of electoral interference and a wave of Trumpism sweeping across Latin America.
Named the "Exército do Lula", Lula's Army in English, the group mobilised millions of Brazilians in support of the incumbent.
How Lula leveraged social youth
Flávio Bolsonaro defied opinion poll predictions on October 4 to shock Lula in an unprecedented first-round election victory with 47 per cent of the ballot.
The result forced Brazil's election to a run-off vote on October 25.
In addressing the first-round loss, Lula pledged to fight, saying: "Tomorrow we start a new campaign."
Lula designated Andre Janones, in yellow, as his social media "general" during his re-election campaign. (Reuters: Amanda Perobelli)
The next day, André Janones, a congressman and federal deputy for the state of Minas Gerais, mobilised the Lula's Army group, which already had 50,000 followers spreading pro-Lula messages.
The posts often included messages of urgency encouraging young voters to "explode" so their voices could be heard and Lula re-elected.
Parts of the content included short calls to arms featuring Janones, who Lula appointed as his social media "general", while some posts featured AI-generated images made to appear like a military was mobilising.
"Attention! Lula's Army is recruiting new soldiers! … To enlist, just leave the following emoji in the comments" one image posted with a saluting emoji said on October 14.
Thousands of Lula's supporters swarmed the streets of Brazil's Sao Paulo after his election victory. (Reuters: Jean Carniel)
After Lula's first-round defeat, young people swarmed the streets of Rio de Janeiro, Sao Paulo and Belo Horizonte with chants such as "Bolsonaro, never again".
This was the crowd Janones wanted to convert into dedicated voters.
Lula's Army ran at odds to Bolsonaro's campaign, which had significant support with more than 16 million Instagram followers.
Oliver Stuenkel, an international relations professor in Sao Paulo, told The Associated Press the group forged an online movement to rival Bolsonaro's internet presence.
"[It] basically embraced the right's style of aggressive politics, very intense, constant messaging," he said.
Flavio Bolsonaro initially refused to acknowledge his election loss. (Reuters: Adriano Machado)
Brazilian political scientist Eduardo Grin said the group leveraged a collective anxiety about Jair Bolsonaro, who was jailed in 2025 for his involvement in a plot to assassinate Lula, and for inciting riots in 2023.
"The mobilisation in the streets and on social media managed to create fear of a return of the Bolsonaro family to power, and concern for democracy and social rights," he said.
Janones convinced Lula to buy his first mobile phone and adopt the moniker "king of the selfie".
Within three days, Lula's Army surpassed 2 million followers, and by election night the group had more than 10.8 million people backing the incumbent.
Lula's promise to improve the lives of workers appealed to young voters. (AP: Lucas Landau)
Voter turnout surged, particularly in wealthier metropolitan centres, but Lula achieved his highest gains in lower-income municipalities where his base was already established.
Crucial to Lula's win were the additional 14.1 million voters who showed up for the second-round election. Analysts say three-quarters of those votes went to Lula, helping him secure re-election.
When the final result was declared, Lula had secured 51.8 per cent of the ballot, with 4.4 million votes more than Bolsonaro.
It marked the first time since 1989 that a candidate lost in the first round and won in the second.
'Fraud' claims after election chaos
Just minutes before polling booths closed, a Supreme Court order was issued to keep stations open for an additional two hours after a request from Lula's campaign.
Lula's team claimed public officials deliberately slowed public transport and hindered voters in Sao Paulo and Salvador, cities that tend to favour the incumbent.
Bolsonaro's side also requested an extension in some areas due to heavy rains in Brazil's south, where he was favoured.
Upon learning of his loss, Bolsonaro refused to accept defeat, saying it was "impossible to acknowledge the result" amid a "dirty trick" by the court.
US President Donald Trump said the result in Brazil "looked like another rigged election". (Reuters: Jonathan Ernst)
In a social media post on Monday, Bolsonaro walked back that commentary by instead pledging to remain in Brazil and spearhead a strong opposition to Lula.
"I am going to gather elected lawmakers and senators to organise our strategy and make the lower house and the Senate our fortress against barbaric acts that are set to happen in another four years of Lula," he said.
US President Donald Trump, who previously lauded Bolsonaro's first-round win as a "big victory", flagged his own issues with the election.
"I didn't take sides, but it looked like another rigged election," Trump told reporters on Monday, local time.
"I just think it had a very bad look, the election, the way it was tabulated."
Bolsonaro's Liberal Party later distanced itself from those claims, saying it acknowledged the run-off result.
Resuming his presidency, Lula now faces an uphill battle in a Congress packed with Bolsonaro allies installed after conservative voters in the first round pushed the Brazilian legislature further to the right.
ABC/Wires