Pollster Datafolha showed the presidential runoff at 50% to 50% in valid votes three days before Sunday's vote. Polymarket's contract on a Flávio Bolsonaro win dipped 2.5 points and recovered half of that overnight.
Brazil's presidential runoff is tied, according to a Datafolha poll released on Thursday evening. Prediction-market traders do not see it that way.
The survey, conducted Oct. 20 to 22 with 2,154 interviews and a margin of error of 2 percentage points, put Flávio Bolsonaro and President Luiz Inácio Lula da Silva at 50% each in valid votes, which exclude blank and spoiled ballots. In total votes, Flávio had 47% and Lula 46%, with 5% blank or null and 2% undecided. A week earlier, Datafolha had shown Flávio ahead 51% to 49% in valid votes and 47% to 45% in total votes.
The runoff is on Sunday, Oct. 25.
On Polymarket, the contract that pays if Flávio Bolsonaro wins traded at 77.9 cents at 3 p.m. Eastern on Thursday. After the poll's release at about 6 p.m., it fell to a low of 75.4 cents at 8 p.m. By 4:48 a.m. Eastern on Friday, it had recovered to 76.65 cents.
Why a 50-50 poll does not mean a 50-cent contract
The gap between the poll and the price is not a contradiction. A poll estimates vote share; the contract prices the probability of winning. A candidate can be tied in one survey and still be the favorite if other evidence points his way.
There is such evidence. Flávio led the first round with 47.03% to Lula's 45.16%. Other recent polls have shown him ahead: Quaest had him at 45% to 44% in total votes, and PoderData and RealTime Big Data both showed him leading 52% to 48% in valid votes in surveys taken Oct. 19 and 20. Traders appear to be weighting the first-round result and the average of polls more heavily than any single survey.
What Datafolha did show is movement. Lula went from two points behind in valid votes to level in a week. The market's 2.5-point dip, about half of which was reversed overnight, suggests traders took note of the trend without treating it as decisive.
The case on each side
The case for the market's view is the first-round result plus a cluster of polls showing Flávio ahead, even if narrowly.
The case for caution is that the race is within the margin of error in every major survey, Datafolha shows momentum toward Lula, and a price in the mid-70s leaves little room for a close race that breaks the other way.
Prices on prediction markets reflect what traders are willing to pay, not an objective probability, and this is one platform.
What to watch
Final polls from Datafolha and Quaest before Sunday, turnout, and the official count on Oct. 25. The Brazilian real and Brazilian equities will be the first financial markets to react on Monday.