Rio De Janeiro: Brazil, like other countries, is facing a very electronic election. WhatsApp, Facebook and Twitter are the weapons of choice to sway the country's 147 million voters - and abuse of social media has been widespread.
Facebook and its WhatsApp messenger service - hugely popular in the Latin American nation - have been thrust into the spotlight for being used to traffic in disinformation.
The extreme-right frontrunner in the run-off election on Sunday, Jair Bolsonaro, has largely eschewed Brazil's established media, preferring to woo voters online in a manner very reminiscent of US President Donald Trump.
Bolsonaro's trailing rival, left-wing candidate Fernando Haddad, has raged against "fake news" and "lies" targeting him and his Workers Party, as Bolsonaro's support has grown into what looks to be an unassailable lead.
Surveys suggest Bolsonaro could pick up 59 per cent of the vote, to 41 per cent for Haddad.
If the race goes in that direction, Brazil - a country that threw off military dictatorship just three decades ago - will veer to the far right, under a president Bolsonaro vowing a relentless crackdown on crime and corruption.
This week, the 63-year-old former paratrooper, a pro-gun lawmaker backed by influential evangelical groups, warned the "red marginals" of the Workers Party "to get out or go to jail".
The language online is just as blunt, mixing truth with lies, or presenting opinions as fact. Many shared posts amplify the Workers Party's past corruption. Others, those backing Haddad, call Bolsonaro a "fascist" bent on destroying democracy.
Accusations of defamation and campaign dirty tricks are flying back and forth. The federal police have opened an investigation into online "fake news" against both candidates.
The potential of social media to influence Brazil's election also evokes the revelations of meddling that came out in the wake of the US election and the Brexit referendum in Britain, both in 2016.
Facebook, its reputation badly marred by those revelations, said on Monday it has closed 68 pages and 43 accounts linked to a Brazilian marketing group, Raposos Fernandes Associates, that media reported was promoting Bolsonaro online on a massive scale.
WhatsApp said it has shuttered hundreds of thousands of accounts to counter "spam or disinformation" after a report saying several companies had been hired for $3 million (Dh11 million) each to send bulk messages attacking Haddad and the Workers Party. Bolsonaro has denied having anything to do with the contracts.
A WhatsApp executive, Victoria Grand, vice president for policy and communications, told reporters in Sao Paulo on Tuesday that the company had no plans to lift a 20-recipient cap for forwarded messages imposed in July, down from a previous limit of 250 recipients.
"We're pretty comfortable with that number," she said, implicitly rejecting a call Bolsonaro made last week for the smaller cap to be overturned.
Grand stated: "I know this is a critical moment for Brazil."
WhatsApp is one of preferred methods for communicating in Brazil. The country, population 210 million, has 120 million WhatsApp users.
Bolsonaro, a previously obscure lawmaker, is a deft user of social media, just like Trump, for whom he has expressed admiration.
After being stabbed last month by a lone assailant, Bolsonaro intensified his online use while convalescing. His Facebook videos, tweets and Instagram posts have millions of followers, far more than Haddad, a 55-year-old former mayor of Sao Paulo who is telegenic but restrained in manner.
Further frustrating Haddad, Bolsonaro has dodged the usual televised debates. Instead of dueling over policies, he has harangued and attacked his rival on the internet.
According to an Oxford University study of Brazil's presidential election, Bolsonaro dominated Twitter conversations and "Bolsonaro supporters spread the widest range of known junk news sources," though Haddad supporters shared the biggest volume.
But Twitter is used by a much smaller, better-informed niche than the more generally adopted WhatsApp.
One of the researchers on the study done by the Oxford Internet Institute, Nahema Marchal, cautioned that it was "extremely difficult to make causal claims between what people see online and how they vote" and that "every election is different."
"Like the US, however, Brazil has seen a number of popular political Facebook groups hacked. There has also been an uptick in political violence, in what has been a bitter and divisive campaign," she told AFP.
While digital technology use differs from country to country, "research indicates that disinformation and conspirational content circulates faster than factual information on social media," she said, in large part because online content "is often the most emotionally-charged".