Polymarket gives Donald Trump good odds – and may have a major fraud problem

More than a billion dollars has been staked about the presidential election on the website Polymarket. But new research says the site is inundated with what’s known as “wash trading,” making the platform appear more popular than it is.

Polymarket currently predicts a 66.1% chance of Donald Trump winning the presidential election. But, according to FortuneBlockchain firm Chaos Labs found that as much as a third of trades can be classified as wash trading, meaning users employ manipulative tactics to make it look like more people are involved than they actually are. Another firm also found signs of laundering, calling into question Polymarket’s odds.

Omer Goldberg, the founder of Chaos Labs, told Fortune that “laundry trading is not specific to Polymarket.” Still, as the platform takes on a bigger role in election predictions, it adds to doubts about how seriously it should be taken as a legitimate indicator of what will happen after Election Day next Tuesday.

The news about laundry trade will come later a Bloomberg report earlier this month found that a small percentage of users who place large bets can easily swing the odds for one candidate or the other. And last week there was a sharp shift in favor of Trump on the platform was credited to a French businessman who bet $28 million on the former president.

Goldberg told Fortune that “identifying and reducing wash trading is critical to ensuring that prediction markets are representative of everyone, with market prices and volumes determined by an authentic, ongoing user base rather than being muddled by inorganic flow.”

Shayne Coplan, who founded the platform, said last week that he believes Polymarket “is a reality check.”

“We’re just market geeks who believe that prediction markets provide the public with a much-needed alternative source of data,” he said on X.

“The beauty of Polymarket is that it’s all peer-to-peer and transparent,” he added. “Even more transparent than traditional finance, where all data is blurred and only visible to the operator.”

Polymarket has not commented on the allegations of laundering.