Polymarket open interest drops 64% after US presidential election

The decentralized prediction market Polymarket saw its open interest plunge 64% following the United States presidential election on Nov. 5, in which Republican Donald Trump was elected as the 47th president. 

Open interest on Polymarket soared to $510.95 million by Nov. 5 and subsequently fell to $184.16 million by Nov. 8, as the Block's Data Dashboard shows. 

Open interest reflects the total value of funds market participants have locked into all active markets on the platform. Higher open interest tends to reflect increased user interest in betting markets. Since the United States presidential election maintained some of Polymarket's biggest prediction markets, the plunging open interest may reflect users redeeming their winnings. 

"Polymarket’s large drop in open interest should come as to no surprise as the platform was heavily reliant on political betting markets, specifically the presidential election," said Steven Zheng, Director of Research at The Block. "With that over now, Polymarket has to find a way to maintain trader interest, whether that’s gearing up for the 2026 midterms or grow its other betting markets like crypto and geopolitical events."

Beating Polls

By Nov. 5, the total betting volume on whether Trump or Democratic candidate Kamala Harris would win the presidential election had ballooned to $3.6 billion, comprising one of the biggest prediction markets on the platform. 

Trump's odds of winning grew to 99% before the race before AP News called him the winner around 5:00 a.m. ET on Nov. 6. Before then, Trump maintained a solid lead ahead of Harris. However, polls often showed a 50-50 tossup of the election's winner. 

"Make no mistake, Polymarket single-handedly called the election before anything else," Polymarket founder and CEO Shayne Coplan wrote on the social media platform X on Nov. 6. 

Coplan previously stated that Polymarket is "strictly non-partisan" and that "prediction markets provide the public with a much needed alternative data source." He explained that if someone feels the current market price for an outcome is overpriced, they can capitalize on what they believe is the undervalued option. 

However, the platform came under fire for alleged market manipulation after a French trader named "Theo" bet a total of $45 million on Trump's win and other outcomes of the U.S. election, which could have biased winning odds toward Trump. Polymarket's investigation into the matter did not find market manipulation, stating that the position reflects the trader's personal view on the election. 

"If someone takes a really big position — on Trump, for example, there’s someone on the other side. There’s a counterparty. It’s all peer-to-peer. So there’s also a really big position being taken on Harris. And because of that, when you see the odds on Polymarket, it’s not a function of how much money was put on either side; it’s a function of market price at that moment," Coplan said on CNBC's Squawk Box on Thursday. “When you think about it like that, some trade that someone made two weeks ago doesn’t have bearing on what the market price is right now.”