More than a billion dollars has been deployed about the presidential elections on the website Polymarkt. But new research says the site is being flooded with what’s known as ‘wash trading’, and that’s making the platform more popular than it is.

Polymarket currently predicts a 66.1% chance that Donald Trump will win the presidential election. But, according to FortuneBlockchain company Chaos Labs found that as many as a third of transactions can be classified as wash trading, meaning users employ manipulative tactics to make it appear as if more people are involved than is actually the case. Another company also found evidence of wash trading, casting doubt on Polymarket’s chances.

Omer Goldberg, the founder of Chaos Labs, told Fortune that “wash trading is not specific to Polymarket.” But as the platform takes on a larger role in election forecasting, doubts are being added about how seriously the platform should be taken as a legitimate indicator of what will happen after Election Day next Tuesday.

The news about the laundry business comes next a Bloomberg report discovered earlier this month that a small percentage of users placing large bets can easily change 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 trader who had 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, sustainable user base rather than confused by inorganic flow. ”

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

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

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

Polymarket has not commented on the wash trading allegations.