ACDC Publishes Final Pre-Midterm Analysis of Election Market Risks

The Anti-Corruption Data Collective published its final pre-midterm analysis on November 2, 2026, reporting that more than $431 million had been wagered on congressional races across Kalshi, Polymarket and Polymarket US. The data was current to October 29, 2026, and covered 28,845 House and Senate markets.

The full briefing, Gambling on Democracy — Briefing 4: A Midterms Update and the Global Picture, excludes governor and mayor races, state-level races and referendums from that total. Kalshi accounts for more than $286 million of the congressional volume. Every congressional race is represented by trades on at least one of the three platforms, and ACDC says the market count is 61 times the number offered for congressional races in 2024.

Price Moves and Knowable Markets

Across 15,985 congressional markets with live order books, ACDC found that 96% could be moved five cents for $3,500 or less, the maximum personal campaign contribution identified in the briefing. Moving a displayed price five cents cost less than $100 in 66% of markets, while 90% of markets had volume below $10,000.

The researchers also examined the most expensive market to move within each of the 470 races with a live order book. In 90% of those races, that market cost less than $25,000 to move five cents.

ACDC calculates that $25.5 million has been wagered on congressional markets classified as “knowable,” where people inside or connected to campaigns could know the answer before the wider public. Mention and endorsement markets are increasing as campaigns hold rallies and make final pushes.

ACDC research fellow Michelle Kendler-Kretsch addressed how those prices should be read during the vote count: “As the counts start to come in tomorrow, the public and the media should remember that prediction market probabilities are susceptible to manipulation and should not be taken as infallible.”

Wallet Concentration and Suspicious Transactions

On Polymarket, ACDC counted 89,453 unique wallets trading congressional midterm markets across 7,397 markets, with typically 48 bettors per market. The top 1% of wallets controlled 75% of volume in the latest analysis, up from 68% in August, while the bottom 50% accounted for 0.2% of bets.

The briefing reports that 79% of trades involved highly capitalized accounts trading more than $1 million across many markets or algorithmic traders operating consistently around the clock.

For suspicious round trips, ACDC screened for a wallet buying at least $500 of a contract priced at 95 cents or above, selling almost all of it within six hours and finishing with less than 1% profit. The screen identified 591 round trips by 544 separate Polymarket wallets in 22 markets, with $618,395 moving through the transactions and total profit of $34.

The transactions had an average stake of $1,046 and an average round-trip time of nine minutes; 44% took less than five minutes, no wallet traded with itself and 92% of the wallets made exactly one trip. ACDC characterized the behavior as indicative of wash trading or money laundering while acknowledging that multiple explanations exist.

ACDC found that for the ten markets with at least 70% of their volume involved in these transactions, the perceived Yes probability was below 4%, and all involved longshot candidates.

ACDC’s Recommended Changes

ACDC argues that Kalshi’s new transparency tools recognize the issues with thinly traded election markets but fall short of providing meaningful new data on price manipulation, foreign interference and wash trading. The platform recommendations are to remove markets on outsider candidates, offer only markets with substantial demand and stop offering markets on inherently knowable questions.

ACDC recommends contractual bans preventing campaign employees and contractors from using prediction markets related to any elections, codes of conduct for volunteers, and legislation assigning jurisdiction over prediction markets to the states.

The briefing leaves the next decisions on market design, campaign rules and jurisdiction with the platforms, political parties, campaigns and lawmakers addressed by those recommendations.