The campaign of President Luiz Inacio Lula da Silva will request the annulment of Flavio Bolsonaro's candidacy on 21 October. Senator Camilo Santana stated the filing would occur on 21 October.

Legal teams for Flavio Bolsonaro filed a court document accusing Lula of "abuse of power" by mass sharing government postings on WhatsApp. Lula's campaign also alleged that Meta suppressed his online content to boost the Bolsonaro family while leaving their content untouched.

The campaign further claimed inconsistencies in the artificial intelligence tool used by WhatsApp. Meta denied taking any actions to favour one side in the election but admitted some of Lula's campaign ads were mistakenly deactivated due to technical errors.

The Superior Electoral Court (TSE) gave Meta 24 hours to prove compliance with an order to treat both campaigns equally, threatening a daily fine of around 200,000 dollars. Meta stated, "We have completed the implementation of the measures to comply with the Superior Electoral Court's decision."

Lawyers from both campaigns and Meta will meet at the Superior Electoral Court on 20 October. Dozens of Lula supporters protested outside Meta's Sao Paulo offices on 19 October.

Lula, who is 80 years old, is seeking a fourth non-consecutive term in office. Flavio Bolsonaro, aged 45, received 47 percent of the vote in the first round, while Lula received 45 percent.

Flavio Bolsonaro swore to liberate his father, Jair Bolsonaro, who is serving a 27-year prison sentence under house arrest. Polls show a technical tie ahead of the runoff on 25 October.

Lula accused the American government of meddling in the elections in favour of Flavio Bolsonaro. Folha de S. Paulo first revealed the information on 19 October.