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Polymarket said that it had linked a single trader to accounts that have wagered heavily on the Republican to win, pushing up his odds on the prediction market.

With the presidential race so tight, election watchers have become increasingly fascinated by political prediction markets, especially as the odds implied by wagers on their platforms suggest that Donald Trump is more likely to win the election.

Questions have arisen about a group of four accounts on Polymarket, one of the most popular platforms, and whether they artificially inflated Trump’s odds there. The start-up told DealBook’s Michael de la Merced that it didn’t believe that to be the case, and provided more information about who’s behind the bets.

The company said that one person was responsible, confirming online speculation. It said that a French national with “extensive trading experience and a financial services background” was the whale behind the accounts — Fredi9999, Theo4, PrincessCaro and Michie — dominating a particular bet about who will win the election. The collective size of the trading positions of the accounts was about $28 million as of Thursday morning, according to data on Polymarket.

Polymarket added that it had made contact with the trader as part of an investigation that was being carried out with the help of outside experts. (DealBook understands the platform worked with Nardello & Company, an investigations firm.)

DealBook hasn’t independently verified the details in Polymarket’s statement, though others have concluded that the four accounts are linked.

Polymarket said it had found no evidence of attempted market manipulation. Instead, it said the trader was “taking a directional position based on personal views of the election.” By spreading out relatively small bets on Trump’s odds, the trader’s goal appeared to be buying up the contract but not suddenly pushing up its price. (Bloomberg Opinion’s Matt Levine has made a similar argument.)

That said, Polymarket added that the person had agreed “not to open further accounts without notice.”

Polymarket said that its contract’s performance was “generally consistent with the price movements on other prediction market platforms.” The contract shows the odds of a Trump victory at over 60 percent Thursday morning. By comparison, similar contracts on PredictIt and Kalshi reflect a slightly tighter spread between Trump’s and Harris’s odds.

Worth noting: Polymarket doesn’t have a primary regulator. The company has been barred from allowing bets by Americans since 2022, as part of a settlement with the Commodity Futures Trading Commission. A Polymarket representative said it hoped to be allowed back in the United States and to be regulated by the agency.

Wagers on the presidential election have taken off in this cycle, especially after claims that these markets are better predictors of the White House race than traditional polls. More money has poured into them after a federal court cleared Kalshi to open up to American bettors.

But the seeming disparity between polls, which show a neck-and-neck race, and the odds on prediction markets has raised questions about potential manipulation to paint an overly rosy picture about Trump’s prospects.

Polymarket stressed in its statement that political prediction markets, which track the odds of a candidate’s victory implied by bets on a platform, aren’t the equivalent to polls, which show how people intend to actually vote.