PoderData's survey gave the opposition candidate a six-point lead over Lula in valid votes. Polymarket stayed at 83.95 cents until midday before rising to 85.15 cents, and Kalshi reached 86 cents on a single block of about 30,000 contracts.
The first national poll since Brazil's first-round vote arrived at breakfast in São Paulo. The contracts tied to the runoff did not react until midday in New York.
A PoderData survey for Aya, published at 7:30 a.m. Brasília time Thursday, showed Flávio Bolsonaro of the Liberal Party with 53% of valid votes against 47% for President Luiz Inácio Lula da Silva in the Oct 25, 2026 runoff. The poll interviewed 3,000 people by phone in 705 municipalities from Oct 5, 2026 to 7 and has a margin of error of 1.8 percentage points. It is registered with the electoral court.
PoderData's last runoff simulation before the first round, conducted Sep 30, 2026 to Oct 2, 2026 with a different sample, had the two candidates tied at 50% each.
How the contracts moved
Polymarket's contract on Flávio winning the presidency held at 83.95 cents from 5 a.m. through 11 a.m. Eastern. It rose to 84.40 cents at noon and reached 85.15 cents by 1:46 p.m.
Kalshi's equivalent contract saw heavy buying early without a price change. A single trade of about 21,700 contracts went through at 84 cents at 6:57 a.m., and about 12,000 more traded at 84 cents at 7:24 a.m. The price did not move until 1:18 p.m., when about 30,000 contracts changed hands at 85 and 86 cents in one burst. It last traded at 86 cents.
At those prices, the contracts imply about an 85% to 86% chance of a Flávio victory. A 53% vote share in one poll is a different measure: it estimates support, not the probability of winning.
Other events in between
The poll was not the only development before the move. Podemos formally endorsed Flávio in the late morning, Eastern time, making it the fifth party to back him, after União Brasil, the Progressistas, Republicanos and Novo. Brazil's electoral court also ruled that the Liberal Party's Douglas Ruas won Rio de Janeiro's governorship in the first round after annulling votes for a rival candidate.
Both arrived after the poll and before the contracts moved. The trading record does not show which, if any, prompted the buying.
The pollster's record
PoderData's final poll before the first round showed Lula ahead in valid votes, 45% to 43%. Flávio won the first round 47.03% to 45.16%. The new survey is a single poll from one firm using phone interviews.
Two views
One reading is that the poll confirms the first-round result and the endorsements, and that event traders, after a week in which party support alone did not lift prices, needed independent numbers before adding to positions.
Another reading is that a six-hour lag and a single large block point to one or a few traders rather than a broad repricing, and that one poll from a firm that underestimated Flávio in the first round is thin evidence for either direction.
Tonight's poll
Datafolha publishes its runoff survey at 5:45 p.m. Eastern on Thursday, based on 2,520 in-person interviews conducted Oct 6, 2026 to 8. It will show whether a second firm finds the same gap. The first televised runoff debate and further polls over the weekend come before the Oct 25, 2026 vote.