Election betting markets are shifting slightly toward Vice President Harris following her debate with President Trump on Tuesday, though Trump is still favored in some election models that are widely considered more predictive of final outcomes. The betting markets could take a dramatic readjustment when national and battleground poll results are released in the coming days. 

Shortly before the debate began, the betting platforms Polymarket and PredictIt had incredibly narrow margins between the two candidates on the question of who would win in November. Polymarket had Trump with a 52 percent chance of winning and Ms. Harris with a 46 percent chance of winning. PredictIt’s model, which measures their bets in terms of cents and not percentages, had 53 cents on Ms. Harris’s victory and 52 cents on Trump’s victory, meaning Ms. Harris was slightly favored. 

Now, Polymarket gives Trump a 50 percent chance of winning and Ms. Harris a 49 percent chance of winning. At her high water mark on Wednesday morning, Ms. Harris had a 50 percent chance and Trump had a 49 percent chance. 

PredictIt quickly shifted in Ms. Harris’s favor on Tuesday night. By midnight, three hours after the debate started, a winning bet on Ms. Harris cost 57 cents, compared to Trump’s 47 cents. By Wednesday afternoon, the odds had narrowed slightly, with a winning bet on Ms. Harris costing 55 cents and a winning bet on Trump costing 48 cents. 

Ms. Harris’s best day on Polymarket was nearly one month ago, when the markets gave her a 54 percent chance of winning to Trump’s 44 percent. Those odds came on August 15, just days before the Democratic National Convention began. Ms. Harris’s best day on PredictIt was just three days earlier on August 12 when a winning bet for her cost 59 cents and a winning bet for Trump cost 43 cents. 

A third website that tracks political bets — Oddschecker.com — has Ms. Harris’s chances of winning at -101, while Trump’s is at +110, which means Trump has a slight advantage in the race. 

Another betting market, Kalshi, will soon start offering bets on the Trump–Harris race after a federal judge overruled the Commodity Futures Trading Commission, which had sought to block the platform from allowing bets on elections. 

Betting on elections has become popular in recent years, though the proliferation of online betting sites and the legalization of the practice in the states across the country has allowed individuals to bet on even the most minute details of every election. On Polymarket alone, more than $92 million was bet on the question of who would be the Republican nominee for vice president, and nearly $130 million was bet on who Ms. Harris would choose as her running mate. 

Both Governor Walz and Senator Kelly had $12 million bet for them that they would be the pick, while $16 million was bet on Governor Shapiro. 

Some other questions that Polymarket users can now bet on include whether or not President Biden will resign from office before the November election, if Trump will increase his share of the Black vote in 2024 compared to four years ago, and whether Ms. Harris will win six critical swing states — Arizona, Georgia, Michigan, Nevada, Pennsylvania, and Wisconsin — in November. 

Even more specific was the question of whether or not Trump and Ms. Harris would shake hands at their Tuesday debate. More than $365,000 was bet on that alone.