Betting markets are souring on President Trump just 48 hours before the 2024 election, despite the fact he has been overwhelmingly favored in the markets for the last two months. Billions of dollars have been wagered on several betting sites during the course of the campaign. 

On these platforms, users purchase either “yes” or “no” options on if a candidate will win the race, meaning that if you buy “yes” on Trump, you are helping increase the cost of future users who want to bet their money on the former president. The cost of those “yes” shares have decreased precipitously in just the last 24 hours. 

The three largest betting markets tracking the 2024 race — Kalshi, Polymarket, and PredictIt — all saw a sharp decline in users purchasing the Trump win stock on Saturday and Sunday. Just one week ago, Trump had a lead on Kalshi of 25 points — 62 percent to Vice President Harris’s 37 percent. On Polymarket, bettors gave Trump a 65 percent chance of winning the race, while on PredictIt, a share of Trump winning cost 61 cents. As of Sunday, it costs just 48 cents on PredictIt. 

A spokesman for Kalshi, Jack Such, shared information with The New York Sun about what is driving Trump’s collapse. Mr. Such called the shift the “most remarkable market activity to date.”

“We’ve now seen Kamala Harris surge all the way back from being 30 percent down 5 days ago to tie the race. With two days to go, this election is officially a coin flip,” he writes. Driving Ms. Harris’s strength in the Kalshi markets are smaller kinds of “sub-bets” where users bet money on individual states. Since October 27, Trump’s odds of winning Pennsylvania have dropped to 50 percent from 61 percent, his odds of winning Wisconsin have dropped to 39 percent from 55 percent, and his odds of winning Michigan have dropped to 35 percent from 50 percent. 

“Her rise in the odds of winning the presidency are mainly tied to the Blue Wall markets, but this isn’t the entire explanation,” Mr. Such wrote in his memo. “Even if she loses one of the Blue Wall states, the markets see her chances of winning other ones to be significantly higher than they were a few days ago. Nevada is now a coin flip. North Carolina is trending towards being a coin flip, with Trump now in the 50’s after being above 70 percent a few days ago.”

Though the markets had been steadily narrowing over the course of the last week, the largest fall Trump has taken was in the wake of a poll from the Des Moines Register and pollster J. Ann Selzer showing Ms. Harris winning Iowa by three points this year. 

On Saturday afternoon, Polymarket gave Trump a 59 percent chance of winning the presidency. After Ms. Selzer’s poll was released at 7 p.m. Saturday, his numbers fell sharply, with Polymarket now giving him just a 54 percent chance of winning. 

“After a string of weeks that featured nothing but Republican momentum, Harris has seen a meteoric rise to claw the race back to a coin flip. With liquidity, activity, deposits, and everything else on Kalshi breaking all-time highs every hour, there’s sure to be more intense market activity all the way through the election,” Mr. Such wrote of Kalshi.