Since he officially entered the contest to run the city of 12 million people after October local elections, the motivational speaker and personal development coach has soared in popularity.
Taking a few leaves from the playbooks of far-right leaders like former president Jair Bolsonaro, US former president Donald Trump, and Argentina's Javier Milei, he paints himself as a political outsider, using provocative rhetoric and slamming the left.
"People want freedom, to say what they think. They don't want to conform to gender ideology. They don't want this 'woke' agenda, which is completely backward," Marcal told AFP, at the end of a day putting up electoral advertising in an affluent neighborhood of Sao Paulo.
His logo is a big blue "M" for his surname, which he and his supporters wear emblazoned onto caps and stickers placed on their T-shirts.
Marcal's campaign for the city, the economic capital of Brazil, has centered on proposals for austerity, banishing "incompetent" workers from the public sector and job creation, especially for the poor.
"He says what many Brazilians would like to say," said Sara Maria Nunes, a 50-year-old nurse, donning the "M" cap.
Stepping on Bolsonaro's toes
Some analysts see Marcal as stepping on Bolsonaro's toes in the ultra-conservative camp.
Despite their similarities, Bolsonaro is backing incumbent mayor Ricardo Nunes, a right-wing politician seen as a more traditional candidate, for which he has faced criticism from his own supporters.
This boosts Marcal's image as the "anti-system candidate," said Jonas Medeiros, research director of the Center for Critical Imagination.
Less than a month to the election Marcal is in a three-way tie with Nunes and Guilherme Boulos, the candidate of leftist President Luiz Inacio Lula da Silva, according to the latest poll from the Datafolha institute.
The son of a civil servant and a domestic worker, Marcal was born in the centre-west city of Goiania. He grew an online following giving motivational talks and money-making courses.
Marcal counts more than 25 million followers across social media networks.
"I am the main digital actor in the country today," he has said.
Local media say he is the wealthiest candidate in the Sao Paulo mayoral race.
However, some of his accounts were suspended by the country's electoral tribunal after he promised to pay followers who created profiles to share his video.
He welcomed the punishment, saying "any persecution accelerates the process" towards victory.
'Essence of the extreme right'
Marcal admits that some of his most controversial statements are a tactic to "grab the attention" of voters and the media.
He has called Lula voters idiots, hinted that one of his rivals was the "biggest" cocaine snorter in the city and threatened to send communists by bus to Venezuela.
"I am not going to apologize for saying what needs to be said. Now, after the electoral period, this war is not needed" against others, said Marcal, who has expressed interest in running for the presidency.
Charismatic and athletic, Marcal is an avowed Christian and is married with four children.
He has been embroiled in several scandals. In 2010 he was sentenced to four and a half years for theft, but never served the full sentence.
"He represents the essence of the extreme right, of hatred, of lies," said rival candidate Boulos.
