As of 5 p.m. EDT on Friday, Trump's probability of winning fell to 64% on Polymarket, a crypto trading platform. The odds are similar to what the betting markets offered him when President Joe Biden dropped out of the race. Betfair Exchange, the UK's largest peer-to-peer betting platform, predicted on its temperature gauge Friday afternoon that Trump was on the verge of a “likely victory.”

Bettors on exchanges around the world have widened the gap between Trump and Harris in recent days as some question whether wealthy players, including Polymarket, could manipulate the markets. Polymarket officials have said they are investigating these claims.

Presidential votes are not the same: Search your state to see how powerful your state is

Trump and Harris' probability of winning each state

Trump's likelihood of winning began to increase in the last two weeks as Harris' poll numbers declined in battleground states. Below are the contested states as defined by Real Clear Politics. The seven states account for 93 of the 538 electoral votes.

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Probabilities are not potential chances of winning

Polymarket has emphasized in its recent “The Oracle” newsletters that the probability of a candidate winning – expressed as a percentage – is not comparable to the percentage of votes a candidate might win in a state.

One way to tell the difference is by looking at the odds for NFL games. BetMGM gives the Chicago Bears a 56% chance of defeating the Washington Commanders this Sunday. The commanders have a 49% chance of winning. That seems like a sizable gap considering the Bears are just 1.5 point favorites to win at BetMGM.

Kamala Harris is leading early voting, a new USA TODAY poll says

Kamala Harris is leading early voters so far among early voters casting ballots in key states, according to a new USA TODAY/Suffolk University poll.

Similarly, as of 5:00 p.m. EDT on Friday, Trump had a 64.1 percent chance of winning the presidential race, based on betting on Polymarket. However, according to a poll aggregated by Real Clear Politics, the gap between Harris and Trump in support in each state remains largely within each poll's margin of error.

Trump's likelihood of winning increases with a narrow lead in the election polls

So are bettors seeing something that pollsters aren't?

Earlier this month, Trump's odds rose slightly when Ohio Senator JD Vance, Trump's running mate, debated Minnesota Governor Tim Walz. Trump's odds of winning skyrocketed early last week as bettors on Polymarket boosted his odds of winning three battleground states: Pennsylvania, Wisconsin and Michigan.

How win probabilities and polls differed between 2020 and 2024

Still, the odds and polls appear to be at odds in the last two elections.

In recent days, Trump's likelihood of winning the 2024 election has moved closer to Biden's in 2020. However, during this election, Biden's exit polls have often been larger than the margin of error in polls aggregated by Real Clear Politics.

Bettors rate Trump's probability of winning higher than in previous elections

Although the bets on Trump and Harris have diverged significantly in recent days, they are below where Trump was on the opening day of the Republican National Convention. As of July 16, his odds of winning against Biden were over 70% on Polymarket and Betfair Exchange.

According to a 2004 article in the Journal of Economic Perspectives, the clear betting favorite only lost twice in the month before the election, in 1916 and 1948. Betting markets also failed to predict Trump's victory in 2016.