More than $58 million was wagered on the outcome of the U.S. presidential election from Friday morning to Monday morning, according to U.K.-based online gambling company Betfair.

With just one day remaining before Election Day, in what could be one of the closest races in history, former President Donald Trump‘s odds have narrowed from 8/15 to 4/5, shifting his chances of winning from 65 percent down to 57 percent, with Friday and Saturday marking the two biggest days on the 2024 election market since it launched.

“Movement on Saturday night was precipitated by a new poll, the highly respected Des Moines Register, that showed [Vice President Kamala] Harris ahead of Trump in Iowa, a state that has not been a swing state in the last two elections,” Betfair spokesperson Sam Rosbottom said.

The Iowa poll from esteemed pollster Ann Selzer revealed Harris leading Trump by 47 percent to 44 percent among likely voters in the ruby red state. Iowa voted for Trump in the last two elections but voted for former President Barack Obama in 2012 and 2008.

“We haven’t seen this sort of drift on an U.S. election winner favorite at this stage of the campaign,” Rosbottom said.

Despite the slip, Trump remains the favorite to win according to Betfair, who put Harris’ odds at 5/4, giving the Democratic nominee a 43 percent chance of winning.

Rosbottom said that the election has been a “blockbuster” event for the betting markets. A total of $218 million has been bet on the site over the outcome of the U.S. election and “we’re expecting plenty more in the next 48 hours,” Rosbottom added.

Newsweek has reached out to the Trump campaign via email for comment.

Betting markets have gained popularity as election predictors, yet their reliability varies. Unlike polls, which survey voters directly, betting markets reflect the sentiments and behaviors of those willing to put money on an outcome. This approach can provide a real-time snapshot of public confidence but is also influenced by external factors, such as recent polls or high-profile events. Studies show betting markets have sometimes accurately predicted winners, especially when large volumes of data are available. However, they are not foolproof and can be swayed by emotions, misinformation, or skewed by participants who are not representative of the broader electorate.

According to the latest polling averages from the polling aggregator, FiveThirtyEight, Harris and Trump are incredibly close in the latest polls, with Harris ahead by less than a point. The last time they were this close in the polls was back in July.

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