Datafolha's first survey since the first round has Flávio ahead 52% to 48% in valid votes, close to Wednesday's PoderData result. Contract prices rose about a cent, and Kalshi's busiest buying came before the poll was out.
Traders on two event venues now give Sen. Flávio Bolsonaro about an 87% chance of winning Brazil's Oct 25, 2026 runoff. The polls behind that price describe a much closer contest.
On Thursday evening, Datafolha published its first runoff survey since the Oct 4, 2026 first round. Among valid votes, which exclude blank and spoiled ballots and the undecided, Flávio of the Liberal Party led President Luiz Inácio Lula da Silva 52% to 48%. Counting every respondent, the split was 49% to 45%, with 5% planning a blank or spoiled vote and 1% undecided.
Wednesday's PoderData phone poll had put the race at 53% to 47%.
Margin and lead
Datafolha's margin of error is two percentage points. The four-point lead in total votes is twice that, which places the candidates in a tie only at the outer edge of the margin, a result the pollster called statistically unlikely. The survey covered 2,520 in-person interviews in 153 municipalities on Oct 6, 2026 and 7.
Averaging the two polls gives Flávio about 52.5% of valid votes. A contract price of 87 cents is not a vote share; it is the market's estimate of the probability of victory. A steady lead of a few points can translate into a high probability, but only if the polls are accurate.
Accuracy
That condition has not held so far this cycle. In Datafolha's final survey before the first round, Lula had 45% of valid votes and Flávio 42%. The count gave Flávio 47.03% and Lula 45.16%, roughly five points better for Flávio than that survey showed. A polling error of similar size in the other direction would erase the current lead.
Other findings
Lula's rejection rate was 46%, three points above Flávio's 43%. About 94% of respondents said their choice was settled. Among voters who backed the eliminated first-round candidates Augusto Cury, Renan Santos, Ronaldo Caiado and Romeu Zema, 46% said they would now vote for Flávio and 32% for Lula.
The regional pattern held. Flávio led 58% to 35% in the South and 50% to 42% in the Southeast; Lula led 61% to 35% in the Northeast.
The tape
Polymarket's Flávio contract went from 85.15 cents on Thursday afternoon to 86.4 cents early Friday, with most of the gain arriving in one step around 3 a.m. Eastern. Kalshi's contract moved from 86 cents to 87 cents, trading in an 85-to-89-cent range.
On Kalshi, the heaviest burst of buying came at 5:05 p.m. Eastern, when about 51,400 contracts traded at 86 and 87 cents. That was 35 minutes before the poll's scheduled 5:40 p.m. release. After publication, sellers were active at the same prices during the evening and again around 2:30 a.m.
Opposing readings
On one view, a one-cent move was proportionate. Flávio won the first round, has added party endorsements and now leads in two independent polls, so the market had little to update.
On another, the price leaves little room for error. The pollster that now shows Flávio ahead missed his first-round share by about five points, and both new surveys were fielded during a week dominated by endorsement news.
Next polls
AtlasIntel and Ipespe are scheduled to release runoff surveys over the next two days. A third poll with a similar margin would test whether the contracts move closer to 90 cents; a narrower result would test how much of the current price rests on the first-round outcome.