ACDC Finds Congressional Election Odds Vulnerable to Cheap Manipulation
A report shows $431 million has been wagered on congressional races, but prices on many markets can be moved for less than $3,500.
The Anti-Corruption Data Collective found 96% of live congressional prediction markets could have their odds shifted five cents for $3,500 or less.
ACDC Research Fellow Michelle Kendler-Kretsch said the concern is what happens when those prices are passed around as evidence that a candidate is winning. "We were actually surprised when we did our initial research in September how cheap it was to move many of these markets," she said.
The findings, published November 2, cover 28,845 congressional markets across Kalshi, Polymarket, and Polymarket US, with betting volumes nearly tripling compared with the 2024 congressional elections.
ACDC’s latest figures show that 66% of live congressional markets could be moved five cents for less than $100, while only 244 required more than $10,000. Even among the most expensive markets within each of the 470 congressional races, 90% could be shifted five cents for less than $25,000.
Kendler-Kretsch said the calculations show what it would cost to move a price, not whether anybody has tried to rig an election. ACDC cannot tell from the trading records alone why someone placed a particular bet.
Kalshi rolled out new transparency tools in October, including low-volume warnings and measures of forecasting accuracy. Kendler-Kretsch said the warnings were useful but also highlighted just how many contracts have little trading activity. "If you have to label that many markets, should you offer that many markets in the first place?" she asked.
She said the new tools still do not show researchers which accounts are placing large orders or how much influence individual traders have over a market. "The data is still the same; it’s just being presented differently, which has positives for users who are unfamiliar, but doesn’t solve the transparency issues in terms of independent auditing of the vulnerabilities and risks," Kendler-Kretsch said.
Polymarket, by comparison, allows researchers to follow transactions through publicly visible wallets. "On Polymarket, I can see the user that did every trade. I can see every trade," she explained.
ACDC’s latest analysis found that the top 1% of Polymarket wallets now account for 75% of congressional trading volume, up from 68% in August. A typical congressional market had just 48 bettors, while only 32 markets attracted more than 1,000 unique participants.
Matt Cepulis, founder and CEO of 3betmedia, said those conditions could be exploited by anyone looking to give a candidate some cheap publicity. "The trade is cheap; the screenshot is the product," Cepulis told Gambling Insider. "A five-cent jump on a thin House market becomes a chart, the chart becomes a post saying ‘momentum is shifting’, and that post reaches far more people than ever look at the order book."
Kendler-Kretsch made a related point about how journalists report election odds. "All you have to do is take a screenshot of the elevated price," she said. "It can last one second; it can last three hours."
Paul Krishnamurty, chief political oddsmaker for BetOnline.ag, disputes the suggestion that inexpensive price movements pose a significant electoral threat. "I would say market moves of a few cents are irrelevant. Not newsworthy or dramatic," he said. "I have never heard any evidence that betting odds or narrative shifts voters."
