TLDR
- Americans have wagered $431 million on congressional prediction markets ahead of Tuesday’s midterms.
- 96% of live congressional markets could be shifted five cents for $3,500 or less.
- The top 1% of Polymarket wallets drive 75% of congressional trading volume.
- Researchers flagged 591 suspicious round-trip trades worth $618,395 that produced just $34 in profit.
- Kalshi has not responded to criticism that its new transparency tools still hide key trading data.
Americans head to the polls on Tuesday for the 2026 midterm elections, and $431 million has already been wagered on congressional prediction markets. New research shows the odds in most of those markets can still be moved for less than $3,500.
The Anti-Corruption Data Collective (ACDC) published the findings on November 2. The report covers 28,845 congressional markets across Kalshi, Polymarket, and Polymarket US.
Betting volume has nearly tripled compared with the 2024 congressional elections. There are also 61 times as many markets as in the last cycle, but the money is not spread evenly between them.
Most Markets Remain Cheap to Move
ACDC found that 96% of congressional markets with live order books could be shifted five cents for $3,500 or less. About 66% could be moved five cents for under $100, while only 244 needed more than $10,000.
The group also looked at the hardest market to move in each of the 470 congressional races. Even among those, 90% could be shifted five cents for less than $25,000.
“We were actually surprised when we did our initial research in September how cheap it was to move many of these markets,” ACDC Research Fellow Michelle Kendler-Kretsch told Gambling Insider. The figures show the cost of moving a price, not proof that anyone tried to rig a race.
Kalshi added low-volume warnings and forecasting accuracy measures in October. ACDC found that 90% of congressional markets across the three platforms had volumes below $10,000, the level Kalshi uses to flag less reliable prices.
“If you have to label that many markets, should you offer that many markets in the first place?” Kendler-Kretsch asked. She said Kalshi still does not show researchers which accounts place large orders, unlike Polymarket’s public wallets.
Kalshi had not responded to a request for comment from Gambling Insider at the time of publication.
Concentrated Trading and Suspicious Transactions
The top 1% of Polymarket wallets now account for 75% of congressional trading volume, up from 68% in August. That is despite 89,453 unique wallets trading across 7,397 markets.
A typical congressional market had just 48 bettors, and only 32 markets drew more than 1,000 participants. The report found that 79% of trades involved heavily funded accounts or algorithmic traders.
Matt Cepulis, CEO of 3betmedia, said a cheap price jump can be used as publicity for a candidate. “The trade is cheap; the screenshot is the product,” he said.
Ben Head, COO of UK bookmaker BetGoodwin, said the $3,500 figure mainly shows how thin the markets are. “When a few hundred dollars is all that’s been traded on a House race, the price you see isn’t a crowd consensus. It’s just the last trade,” he said.
A Brennan Center for Justice survey found respondents were 10 to 20 percentage points more likely to believe a market-favored candidate would win. It did not show that people vote differently because of the odds.
ACDC also identified 591 suspicious round-trip trades across 22 Polymarket markets, involving 544 wallets. About $618,395 changed hands for a combined profit of just $34.
More than 100 of those trades, worth nearly $250,000, went through the market for Robert Lebovics, a New Jersey Republican Senate hopeful with about a 3% implied chance of winning. ACDC has not established that the trades involved wash trading or money laundering.
The report flagged $25.5 million wagered on contracts tied to outcomes campaign insiders could know in advance, such as endorsements. It also warned that foreign actors could use the markets to spread misleading narratives, though it found no proven foreign operation.
After the votes are counted, ACDC plans to review markets where prices conflicted with polling. Researchers want to find out whether certain accounts repeatedly pushed prices in the wrong direction.
