A new Gambling on Democracy briefing by the Anti-Corruption Data Collective (ACDC) warns that there may be more cases of insider training on election prediction markets than those already reported in the media. ACDC finds that $20.5 million has been traded on congressional midterm election markets with the highest risk of insiders having critical information before it reaches the public. The anti-corruption organisation warned that platforms are incentivising trading on insider information by campaign and election insiders, said that Congress should ban election markets.
ACDC’s analysis finds that the number of midterm election markets in which political insiders can either know in advance or determine the outcome is up 242-fold compared to the last midterms: from just three in 2024 to 725 in 2026. This is partly due to platforms offering far more markets on elections, often in response to breaking news stories and their consequences. The number of markets per race has exploded: from an average of 4.5 in 2024, to 44.4 different markets per race this year.
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The longshot win rate – the percentage of high volume ($2,500) low probability (35 cents or lower) bets that are made on the correct outcome – on knowable markets that have already settled was 24.2%, compared with 14.9% for markets whose outcomes were determined by the public.
ACDC noted that markets on voting results are less susceptible to insider trading on the final outcome. However, because prediction markets allow users to buy and sell positions in real time before markets resolve, political insiders still have an opportunity to profit in advance of changes in sentiment caused by a poll, scandal or endorsement. ACDC identified 186 instances on Kalshi where trading significantly shifted prices just before a public event. This includes 155 cases ahead of a poll being released.
The briefing ACDC pointed to two case instances in which trading patterns before the release of polling and before a candidate exited a race could indicate the use of non-public information.
In the Kentucky 4th Congressional District – one of the most heavily traded races in the 2026 midterms – two wallets roughly doubled their money buying Polymarket contracts that Ed Gallrein would win the Republican nomination in the hours before three polls were publicly released on May 12, 15 and 16, respectively.
On Kalshi on July 5, 27 trades by an unknown number of users bet $1,659 that Maine Democratic Senate candidate Graham Platner would drop out of his race, at markets priced at just 2 cents at the time. The next morning $1,683 was bet across 24 trades over 20 minutes. Twelve minutes later, reports came in that Platner was cancelling his campaign events. That afternoon, Politico published an exclusive story with sexual assault claims against Platner, leading to his campaign being suspended on July 8.
ACDC highlighted that it is difficult for researchers and investigators to prove that any trades are based on the abuse of insider information, and that such behaviour may not breach any rules, even if proven. Cases to date have involved platforms banning or fining candidates who bet on their own elections.
Michelle Kendler-Kretsch, research fellow at ACDC, said:
“The CEOs of Kalshi and Polymarket have said that insider information is “fair game” as long as it is legal, or part of what makes their platform “cool.” But multiple surveys have shown that most Americans are not comfortable with politicians and future public servants turning a profit on information they access before it goes to the public. Platforms should act responsibly and stop offering election markets that incentivise trading on insider information. If they won’t, Congress should listen to Americans’ concerns: ban government employees and campaign staff from trading on prediction markets, and ban prediction markets on elections.”
David Szakonyi, Co-Founder of ACDC, said:
“We’re seeing a startling lack of leadership on this issue from political parties and election regulators. Sports leagues seem to be putting far more pressure on the platforms not to offer markets that can put the integrity of the game at risk. We can’t leave something as critical as America’s elections simply to platforms to police for user activity that breaches their terms and conditions. We need lawmakers and regulators to catch up with reality and impose rules and transparency on giant tech companies that are inviting gambling on our democratic process.”
ENDS
Notes to editors:
- Download the full briefing here: http://acdatacollective.org/wp-content/uploads/2026/10/Gambling-on-Democracy-Briefing-3_Insider-Information-in-Election-Prediction-Markets.pdf
- ACDC has updated its Gambling on Democracy dashboard with new data on congressional midterm elections on prediction markets with data current to 30 September. See https://acdatacollective.org/work/gambling-on-democracy/ for details.
For media enquiries: team@acdatacollective.org
Gambling-on-Democracy-Briefing-3_Insider-Information-in-Election-Prediction-Markets.pdf