Trailing leftist candidate Fernando Haddad accused the far-right frontrunner, Jair Bolsonaro, of “illegal” electoral tactics after a report that companies were poised to unleash a flood of WhatsApp messages attacking him and his Workers Party.

Bolsonaro denied the allegation, tweeting that the Haddad’s Workers Party “isn’t being hurt by fake news, but by the TRUTH”.

The exchange happened 10 days before a run-off election that polls predict Bolsonaro – a bluff, internet-savvy, pro-gun polemicist often compared to US President Donald Trump – will likely win comfortably.

Ordinary Brazilians told AFP they got much of their election information through WhatsApp. They said some in their families or entourage swallowed some misinformation but denied they themselves were being influenced.

“We get a lot of news, even false news, but some true, about politics but I don’t think it changes very much in terms of making decisions,” said Ana Clara Valle, a 27-year-old engineer in Rio.

She said she was voting for Bolsonaro because of his Catholic, pro-family stance, not because of any “extreme right” sensibility.

Andre de Souza, a 35-year-old lawyer leaning towards voting for Bolsonaro, said he receives around 500 WhatsApp messages a day for and against both candidates.

The rumuors and false information “don’t make a difference to me”, he said, but added: “My mother received a WhatsApp message saying Bolsonaro was doing away with (mandatory) end-of-year salary payments, and she believed it!”

Haddad made his accusation after Brazil’s widest circulation newspaper, Folha de Sao Paulo, reported it had discovered contracts worth up to US$3.2 million (RM13.5 million) each for companies to send out bulk WhatsApp messages attacking the Workers Party.