Polymarket's runoff contract rose to 80.1 cents from about 77 cents between 3 p.m. and 7 p.m. Eastern on Tuesday, with no specific catalyst identified. Five recent polls differ on how close the race is; two show his lead outside their margins of error. A new Datafolha poll is due Thursday, three days before Sunday's vote.
Four days before Brazil's presidential runoff, the betting market has moved further than any single poll would justify on its own.
On Polymarket, the contract on Flávio Bolsonaro winning the presidency traded at 80.1 cents at about 4:48 a.m. Eastern on Wednesday, up from about 77 cents on Tuesday morning. The price implies about an 80% chance that he defeats President Luiz Inácio Lula da Silva on Sunday, Oct. 25. A comparable Kalshi contract stood near 79% at 8 a.m. on Tuesday.
A move without a clear trigger
The timing of the rise is the first puzzle. A Real Time Big Data poll showing Bolsonaro ahead 52% to 48% in valid votes, or 48% to 45% including all responses, was published by about 6:30 a.m. Eastern on Tuesday. The Polymarket contract barely moved for most of the day, holding between about 76.6 and 77.1 cents until around 3 p.m. It then climbed through the evening, reaching 77.85 cents at 4 p.m., 78.45 cents at 6 p.m., 80.1 cents at 7 p.m. and 80.85 cents at 8 p.m. No evening catalyst was identified.
A rise that starts about nine hours after a poll is hard to credit to that poll. It points instead to positioning, or to traders acting on information that has not surfaced publicly.
What the polls show
The surveys are close, but most point the same way. Datafolha's Oct. 15 poll had Bolsonaro ahead 51% to 49% in valid votes, inside its 2-point margin of error. Vox Brasil, on Oct. 18, had Lula ahead 51% to 49%, also inside its margin. Real Time Big Data's 52% to 48% lead sits at the edge of its 2-point margin.
Two polls put Bolsonaro's lead outside the margin. AtlasIntel, on Oct. 19, had him at 51.1% to 48.9%, with a margin of 1 point, and PoderData had him ahead 52% to 48%, with a margin of 1.8 points. Quaest, Gerp and MDA surveys also showed him in front.
Reading the 80%
A consistent narrow lead across most pollsters can support a high market price, because a market prices the chance of winning, not the size of the margin. A candidate who is ahead by 2 to 4 points of valid votes in nearly every survey can be a clear favorite even if no single poll shows a commanding lead.
The market is deep enough to take seriously. The contract had about $582,000 of liquidity and more than $620,000 of trading in the previous 24 hours. But election prices also reflect who is trading, and Tuesday's evening climb came without a public trigger.
Market implications
One reading is that traders are pricing the consistency of Bolsonaro's polling lead correctly. Most surveys put him ahead, two of them outside their margins of error.
A second reading is that the market is overconfident. Two of the most widely cited polls, Datafolha and Vox Brasil, still show a race within the margin of error, and one has Lula ahead.
What to watch
Thursday's Datafolha poll, based on 2,250 interviews conducted from Oct. 20 to Oct. 22; other final polls; the Polymarket and Kalshi prices into the weekend; and the result on Sunday. A Datafolha reading with Lula ahead would test whether the market's 80% holds against one of the most closely followed surveys.