Senators give Kalshi and Polymarket an Election Day deadline on insider trading and wash trading

What did the senators ask Kalshi and Polymarket?

According to the senators' release and press coverage, the questions cover ^{[2] [4] [5]}:

• how each company stops candidates, campaign staff, election officials, pollsters and others with material non-public information from trading — including through third parties or affiliated accounts;
• how they detect wash trading and other coordinated activity that can move a contract's price or inflate its reported volume;
• how many suspected insider-trading or manipulation cases on election contracts they have found since 1 January, how many were stopped before a trade rather than discovered afterwards, and how many were referred to the CFTC or law enforcement;
• whether outside evaluators have reviewed their surveillance systems, what extra safeguards they will add before the election, and how they keep election contracts from being mistaken for polling.

The letter points to cases of candidates trading on their own races on Kalshi — a 2025 case described in a CFTC advisory and three more disclosed in April 2026 — and to a 2024 Fortune report in which a blockchain-analytics firm estimated that roughly a third of Polymarket's presidential-market volume was likely affected by wash trading. It also cites NPR reporting on campaign insiders trading before polling was released ^{[2] [6] [7]}. The senators wrote that "the identification of isolated instances of improper trading does not demonstrate that these markets are adequately protected" ^[1].

How have the companies responded?

Kalshi's head of enforcement, Robert DeNault, said the exchange prohibits insider trading and market manipulation and proactively blocks candidates and campaign staff; Kalshi says it matches Federal Election Commission payroll data against its identity-verified users, runs real-time surveillance and has formed an independent market-integrity committee ^{[6] [4]}. Polymarket told The Epoch Times it monitors election activity with its "Polygraph" tooling, and its head of investigations told NPR the company had looked into "dozens" of midterm bets ^{[4] [5]}. At the time of writing (3 Nov 2026, 01:30 UK time) we found no public release of either company's written answers.

What does it mean for prediction-market and odds data?

Our analysis. The letter is not a rule change, but it targets the two numbers most dashboards and AI agents lean on: price and volume.

• Volume is a weak quality signal. If part of a market's volume can be wash trades, "most traded" does not mean "most reliable". Order-book depth, spread and how long a price holds are harder to fake than a headline volume figure.
• Cross-venue comparison is an integrity check. When the same event trades on several venues, a price that diverges sharply from the others — or moves without news — is worth flagging before you treat it as information. Doing that needs normalised prices from many venues side by side: Odds-API.io Partner link returns Polymarket and Kalshi prices (with back/lay depth) alongside 450+ bookmakers through one API — see its prediction-markets guide ^[8].
• Keep timestamps. Election nights bring fast information shocks. Storing time-stamped snapshots lets you check later whether a move came before or after public news — the same question regulators ask.
• Markets are not polls. The senators explicitly ask how contracts are kept from being confused with polling. If you feed market prices to a model, treat them as one noisy, money-weighted signal, not as a measure of voter intention.
• Regulatory overhang. Kalshi notes that Congress is considering making it a crime for campaign staff to trade on their own races ^[4]. Answers that look thin could feed that push, which would affect which election markets exist at all.

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