Seven days before the runoff vote, Flávio Bolsonaro and Luiz Inácio Lula da Silva met on a debate stage for the first time, exchanging sharp remarks throughout the Sunday encounter. Pre-debate polling placed Bolsonaro — son of former President Jair Bolsonaro — ahead heading into the October 25 runoff, with a margin of nearly two percentage points over Lula from the first round of voting earlier that month underpinning that assessment.

Poll data pointing to a tightening contest has accompanied statements from Lula that he believes he can become the first candidate to place second in an opening round and still claim victory since Brazil restored democratic rule in the 1980s. Speaking with reporters ahead of the debate, Lula expressed his aim of drawing support from the roughly 33 million people who did not cast a ballot in the first round — a pool representing approximately one in five of those eligible to vote.

The forum-style event, which featured minimal moderator intervention, gave candidates freedom to move around the stage and address one another directly. The exchange centred on mutual allegations of wrongdoing and pointed personal remarks.

During the televised encounter — the first time Lula and Bolsonaro had faced each other after both had passed on earlier opportunities — Lula raised questions about Bolsonaro's reported ties to imprisoned banker Daniel Vorcaro, while Bolsonaro put forward allegations concerning Lula's son and a pension fraud matter. Each candidate also exchanged pointed personal characterisations of the other, with Lula attributing dishonesty to the Bolsonaro family and Bolsonaro asserting that Lula carried a longstanding association with corruption.

Heated exchanges between participants, along with audible crowd reactions, were partly attributable to the structure of the event itself. Bolsonaro moved around the stage behind Lula during the latter's speaking turns — behaviour that debate organisers deemed permissible under the rules, though Lula's camp lodged objections. Lucas de Aragão, a partner at the Brasília-based consultancy Arko Advice, offered the view that Bolsonaro held a modest overall edge, attributing it more to body language than to the substance of his arguments, and noting that Lula appeared ill at ease for much of the exchange.

During the campaign exchange, Lula chose not to stand alongside Bolsonaro, describing him as a "militiaman" — a term that pointed toward longstanding allegations connecting the senator to paramilitary networks operating in Rio de Janeiro. Bolsonaro then remarked that he was relieved to have left his wallet at home — a comment widely read as a reference to the corruption case that had resulted in Lula's 2017 conviction, a ruling subsequently overturned.

Policy positions put forward by the contenders drew from pre-election pledges, with little new ground covered across the debate. Among the commitments Bolsonaro put forward was a plan to formally classify the country's criminal gangs and armed militias as narco-terrorist organisations, alongside a proposal to add more than 500,000 new prison places. Minimum wage adjustments that outpaced inflation during his time in office were cited by Lula as evidence of a broader economic approach centred on distributing purchasing power across a wider share of the population rather than concentrating it at the top.

Food costs drew particular attention in the candidates' debate, with grocery prices featuring prominently given that Lula's approval ratings had softened on the issue despite a drop in inflation and unemployment reaching a record low. One candidate put it plainly, asking whether people were paying more or less at the checkout than before. Bolsonaro posed a question to the crowd about how recently they had last been able to stock their freezer with meat.

Each contender levelled charges against the other of undermining the country's sovereign interests. Lula alleged that the Bolsonaro family had pressed Washington to levy tariffs against Brazil and that its members wanted the country to struggle economically, adding that the family's conduct placed foreign interests ahead of those of the Brazilian people. Bolsonaro pushed back against Lula's assertions, contending that Lula's tenure had left Brazil answerable to globalist and terrorist interests.

The day also saw Bolsonaro's backers gather along São Paulo's Paulista Avenue, Lula's supporters assemble in the plaza at the centre of Brasília's government district, and students take to the streets of Rio de Janeiro in opposition to Bolsonaro. The protests brought into view the accumulated tensions driving the political divisions that have kept Brazilian governance at an impasse for close to ten years.

Bolsonaro's base has long called for Lula to face prosecution over the graft allegations that dogged his Workers' Party, a demand that remains a fixture of their political grievances. Bolsonaro's conviction on coup-related charges drew expressions of approval from a portion of his political rival's base, though views on the verdict vary across the broader public.

Protesters in São Paulo raised a large inflatable figure depicting Lula dressed in prison clothing. Vera de Sousa, one of the demonstrators present, called for Lula's removal from office. Demonstrators gathered in Brasília called for the former president's imprisonment and displayed an effigy depicting him with bloodied hands, while one attendee told reporters that keeping the current government in office was a priority.

Sonia Maria, who backs Lula, said a change in government would leave the country in a very bad position. A corruption conviction that courts later voided — citing procedural and investigative irregularities — kept Lula behind bars for 580 days across 2018 and 2019.

A Brazilian court handed Bolsonaro a 27-year prison term, finding that he had orchestrated efforts to overturn the 2022 election result that ended his presidency and brought Lula to power. His detention is being carried out at his residence on medical grounds. Eduardo Bolsonaro has characterised his father's legal proceedings as a sham and has indicated he would pursue a pardon for the elder Bolsonaro should he win the presidency.

Another face-off between the candidates is scheduled for October 23, in the days leading up to the runoff vote.