Who will win the Brazilian presidential election in October 2026?

The Brazilian presidential election is scheduled for October 4, 2026, with a potential runoff on October 25, 2026. This question asks to predict the winner of this election.

Forecasted on

Resolved forecast

Status: Resolved

Outcome: Luiz Inácio Lula da Silva

Resolved on

Resolution reasoning

Multiple independent, authoritative Brazilian news sources citing TSE (Tribunal Superior Eleitoral) data confirm that Lula won the October 25, 2026 presidential runoff against Flávio Bolsonaro. With nearly 100% of ballots counted, outlets report Lula secured approximately 51.77%-51.79% of valid votes versus approximately 48.21%-48.23% for Flávio Bolsonaro, reversing Bolsonaro's first-round lead. Sources including InfoMoney, TRE-SP (an official regional electoral tribunal), CNN en Español, and others consistently report this result and declare Lula re-elected for his fourth presidential term.

Resolution criteria

Resolves based on the official results of the Brazilian presidential election, as certified by Brazil's electoral authority (TSE). If a candidate wins an outright majority in the first round on October 4, 2026, that candidate is declared the winner; otherwise the top two candidates proceed to a runoff on October 25, 2026, and the runoff winner is declared the winner of the election.

Historical forecast probabilities

  • Luiz Inácio Lula da Silva: 99.4%
  • Flávio Bolsonaro: 0.5%
  • Someone else: 0.1%

Reasoning

Lula da Silva is the overwhelming favorite because the election is no longer unresolved: Brazil’s electoral authorities declared him the winner of the runoff. The probabilities are Lula 99.4%, Flávio Bolsonaro 0.5%, and someone else 0.1%.

Lula: The counted votes settle the question

Flávio Bolsonaro led the first round, taking 47.03% to Lula’s 45.16%, but neither won a majority [e1608, e1641]. In the runoff, Lula reversed that deficit, winning 51.8% of valid votes to Bolsonaro’s 48.2%—a margin of roughly four million votes [e1618, e1629]. The Superior Electoral Court declared Lula the winner, and multiple reports confirm the result [e1625, e1633, e1635]. It is a striking outcome: Lula became the first candidate since Brazil adopted its two-round system to win the presidency after finishing second in the first round [e1616].

The pre-election picture helps explain why the contest was close, not why the result remains uncertain. Polling had converged on a near-tie, while the first-round count gave Bolsonaro a narrow lead. But once the runoff was counted, that earlier uncertainty was overtaken by the actual result.

Flávio Bolsonaro: A challenge, but no demonstrated basis to overturn the result

Bolsonaro refused to concede and said he would seek annulment, pointing to the nationwide extension of voting hours [e1617, e1621]. Yet both campaigns had requested additional voting time, and the TSE said the election was conducted correctly [e1650, e1646]. The challenge is a reason to reserve a small probability for an unexpected legal reversal, not to treat the declared result as genuinely in doubt.

Someone else: Almost no plausible route

No third candidate can plausibly be treated as the winner of a runoff that was held between Lula and Bolsonaro and whose result has been declared by the electoral court [e1660, e1625]. A different winner would require an extraordinary chain of events, such as annulment followed by a new election, for which the available evidence offers no meaningful support.

Why these probabilities

A counted runoff and an official declaration outweigh pre-election polling, first-round results, and a losing candidate’s unsupported challenge. The reported caveat about formal declaration does not outweigh the court’s reported announcement of Lula’s victory. That leaves 99.4% for Lula, 0.5% for Flávio Bolsonaro, and 0.1% for someone else: near certainty, with only a sliver reserved for an exceptional reversal.

Update summary

Lula won the runoff with 51.8% of valid votes, reversing Flávio Bolsonaro’s first-round lead, and Brazil’s Superior Electoral Court declared him the winner [e1618, e1625]. Bolsonaro said he would seek annulment, but the court said the election was conducted correctly [e1617, e1646].

Cited evidence