Why Flávio’s Odds Collapsed on Polymarket
BRAZIL · ELECTIONS
Published Sunday, 25 October, 5:45 p.m. ET (9:45 p.m. Lisbon) · Source: Polymarket data, Kalshi, Betfair, PredictIt, Chainalysis, TSE
Key Facts
- The price Polymarket’s Flávio contract fell from 81.9% (1:30 p.m. ET) to 64.9% (4:51 p.m. ET) on Sunday.
- Order book about US$41,000 of selling would move the price 19 points; 612 trades, about US$87,000, drove the slide.
- Method we examined four things, found no single large order, and cannot prove or rule out manipulation.
- Watch the TSE count, paused at 0.25% at 4:20 p.m. ET; only TSE results decide the winner.
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Prediction markets · who wins the runoff
Implied chance of winning Brazil’s presidency on 25 October, from traders’ prices.
Polymarket
Flávio Bolsonaro 67% · Lula 33.6% (US$202 million traded)
Kalshi (regulated in the US by the CFTC)
Flávio Bolsonaro 69% · Lula 32%
As of 25 October, 5:20 pm ET (21:20 Lisbon), updated every 20 minutes. Prices are bets, not polls, and can move fast.
Why we show this: prediction markets turn real-money bets into a live probability that moves within minutes of the news, which is why investors, campaigns and newsrooms in the United States now follow them closely. We show them next to polls and official results, never instead of them.
Flávio Bolsonaro’s price on Polymarket, an online prediction market where users trade contracts on outcomes, fell about 19 percentage points in under a day.
Polymarket puts Flávio Bolsonaro’s chance of winning at 67% and Kalshi at 69% (Lula: 34% and 32%), as of 25 October, 5:20 pm ET; prices are bets, not polls. See our live Brazil election odds page and official results.
What the Price History Shows
Polymarket’s public price history peaked at 83.9% at 7:45 p.m. ET on Saturday, 24 October. On Sunday it stood at 81.9% at 1:30 p.m. ET, 71.2% at 4:15 p.m. ET and 64.9% at 4:51 p.m. ET.
The sharpest leg ran from 4:06 p.m. ET (76.1%) to 4:12 p.m. ET (64.9%), about 11 points in six minutes. The price recovered to 70.3% by 5:10 p.m. ET.
The Superior Electoral Court (TSE), Brazil’s election authority, paused its count at 4:20 p.m. ET, after the slide began. See our voting extension and count pause reports.
How a Thin Market Moves
The order book is the list of standing offers to buy and sell. When the offers near the current price are small, a modest sale uses them up and the next trade happens at a worse price.
At 5:15 p.m. ET, about US$30,000 of selling would have pushed the price down 5 points and about US$41,000 down 19 points. The slide ran through 612 small trades totalling about US$87,000 between 4:06 and 4:13 p.m. ET, the largest about US$4,800.
Pushing the price up would have cost more: about US$100,000 of buying for 5 points and US$125,000 for 10 points. This is the book at 5:15 p.m. ET, not at 4 p.m., so it may not show how deep it was during the slide.
Who Is on the Other Side
Every trade has another side, often a market maker, a participant who posts standing offers to buy and sell and earns the gap between prices.
Was It Manipulated?
We examined four things: public trades in the slide window, the order book, any pullback afterward, and news reports of allegations. We found no whale, meaning a very large single trader: the largest trade was about US$4,800, and the five largest trades in the 4 to 5 p.m. ET hour made up 8% of volume.
The news search found no allegation or investigation. This analysis cannot prove or rule out manipulation.
Precedents for Fast Moves
Betfair priced a Remain vote at about 90% on 23 June 2016 and Leave above 60% the next morning, PredictIt moved Donald Trump up more than 40 points to about 65% on US election night 2016, and Polymarket had him at 99.1% by 1:30 a.m. EST on 6 November 2024. Sunday differed: the TSE had published only 0.25% of votes.
How to Bet
On Polymarket a user buys “Yes” or “No” shares with a dollar-backed token through a crypto wallet, and each share pays US$1 if the outcome happens. Kalshi, a US exchange regulated by the CFTC, uses dollars and identity checks.
Limits of This Analysis
The trade list we used totals less than the US$4.1 million Polymarket reports for the last 24 hours, so our figures are minimums. We do not know the order book during the slide, or what traders reacted to.
More: Brazil news in English, every day from The Rio Times.
Frequently Asked Questions
Why did Flávio Bolsonaro’s odds fall so fast?
A thin order book: about US$41,000 of selling could move the price 19 points.
Was the Polymarket price manipulated?
We found no single large order. This analysis cannot prove or rule out manipulation.
Does the price show who will win?
No, it is the level at which traders are willing to buy and sell. Official results come only from the TSE.
Sources: Polymarket public data at 5:15 p.m. ET, 25 October 2026; Kalshi; Betfair; PredictIt; TSE.
This article was produced by The Rio Times’ automated newsroom system. How we use AI · Report an error · Editorial responsibility: Matthias Camenzind, Editor-in-Chief