Brazil Electoral Forecast
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Published on 23 September 2026
Forecast sealed before the general election in Brazil of 4 October 2026: Presidency, 27 governorships, 54 Senate seats and 513 Chamber seats. Information cut-off: 22 September.
✓ Verifiable timestamp (OpenTimestamps)
Forecast sealed before the event
Central first-round estimate: Flávio Bolsonaro 44.5% of the valid vote and Lula 41.5%; Flávio finishes first in 77.46% of simulations. The model and the polling signals disagree over first place. A runoff is almost certain, and neither principal presidential bloc would hold its own majority in the Chamber.
Official result
Flávio Bolsonaro finished first with 47.03% of valid votes against 45.16% for Lula, a 1.87-point margin (the sealed central estimate was 44.5% against 41.5%), as we forecast with a 77.46% probability and against all five polls, which had Lula ahead. There is a runoff (99.3%) and turnout, 78.92%, fell inside its band (78.5-81.1%). In the Chamber, 9 of the 14 party families landed inside their ranges; União Progressista (87 vs 113), PL (121 vs 104), Republicanos (41 vs 55), Federação PSOL REDE (15 vs 10) and Novo (10 vs 3) missed. Source: Superior Electoral Court (TSE).
Direction: HitMagnitude: Miss
Independent verification
This document was timestamped before the event it forecasts — sealed 11 days before the event. The proof does not depend on Oliveira Vantage: anyone can check it without asking us for anything.
SHA-256 fingerprint of the document
a9062dab 66e864d3 6ba6e638 995f4dc4 ac2c5dcd 974bc556 d2851b97 3456cce7
Status: anchored in the Bitcoin blockchain
Calendars: alice.btc.calendar.opentimestamps.org, bob.btc.calendar.opentimestamps.org, finney.calendar.eternitywall.com
Seal date: 23 September 2026 · event: 4 October 2026
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