Things were heated but remained civil on screen, which cannot be said for the sidelines in the press room where tensions erupted into the open between the Lula and Bolsonaro entourages.
Sparks flew on TV as far-right President Jair Bolsonaro accused leftist rival Luiz Inacio Lula da Silva of massive corruption –– and drew accusations of "destroying Brazil" in return –– as they faced off in their first election debate.
The two front-runners, who waited until the last minute to confirm they would attend the first televised debate ahead of October's elections on Sunday, wasted no time in attacking each other in Sao Paulo.
Bolsonaro called Lula a "thief" in his opening salvo, pummeling the 76-year-old ex-president over the massive "Car Wash" corruption scandal centred on state-run oil giant Petrobras.
The investigation landed Lula in prison from 2018 to 2019 on controversial corruption charges – annulled by the Supreme Court last year.
"Your government was the most corrupt in Brazilian history," said Bolsonaro, 67, rattling off figures from the Petrobras scandal in a rapid-fire attack.
"It was a kleptocracy, a government based on robbery.... What do you want to come back to power for? To do the same thing to Petrobras again?"
Lula fired back that Bolsonaro was spreading "untruths" –– one of several exchanges in which they accused each other of lying –– and in turn, accused the incumbent of trashing the legacy of economic growth and anti-poverty initiatives that Lula left as president.
"This country has been destroyed," he said in his trademark gravelly voice.
Heated on the sidelines
Dressing the part in dark suits and ties –– striped blue for Bolsonaro, red for Lula –– the front-runners had numerous fiery exchanges but hewed to the rules and kept their demeanor relatively civilised.
But tension erupted into the open in the press room where their entourages were watching.
Pro-Lula lawmaker Andre Janones and Bolsonaro's ex-environment minister Ricardo Salles got into a ferocious shouting match and had to be pulled away from each other.
In all, six of the 12 presidential candidates on the ballot were on the neon-blue-lit stage.
But all eyes in the deeply polarised South American giant of 213 million people were on front-runner Lula, the popular but tarnished ex-metal worker who led Brazil from 2003 to 2010, and his nemesis, Bolsonaro, the leader nicknamed the "Tropical Trump," who is vying for a come-from-behind win.
Lula leads Bolsonaro by 47 percent to 32 percent, according to the latest poll from the Datafolha institute.
If no candidate wins more than 50 percent of valid votes in the first round on October 2, the election will go to a run-off on October 30.
READ MORE: Thousands rally in Brazil in 'defence of democracy'