LAS VEGAS — Gamblers are not liking Mike Bloomberg's odds.
The former three-term New York mayor is plummeting in online betting markets one day after taking a two-hour pummeling from his Democratic rivals during his first appearance on a presidential debate stage.
Bloomberg dropped from 25% to 20% on PredictIt as of Thursday, a top online betting platform established by researchers in New Zealand. Bloomberg's odds on PredictIt dropped as low as 16% during the debate itself.
On Smarkets, a U.K.-based online gambling platform, Bloomberg's odds were sliced in half, dropping to under 15% on Thursday from an all-time high of more than 31% ahead of the nationally televised event.
Sen. Bernie Sanders, I-Vt., who is the race's front-runner according to recent national polling, saw a boost in his odds after Wednesday's Democratic debate. Both platforms give Sanders about a 50% chance of securing the nomination as of Thursday.
Former Vice President Joe Biden, Sen. Elizabeth Warren, D-Mass., and former South Bend, Indiana, Mayor Pete Buttigieg also saw bumps in their odds. On PredictIt, Biden rose to 12% on Thursday from 10% the day before, Buttigieg climbed to 11% from 8%, and Warren jumped to 7% from 3%.
In another measure of debate performance, both Sanders and Warren claimed their biggest debate-day hauls of the race on Wednesday, taking in more than $2.5 million each. Warren narrowly out-raised Sanders.
U.S. financial markets, which trade far more volume than political betting markets, are still pricing in a Trump victory in 2020. But Sanders' performance Wednesday night, amid calls to overhaul the health-care industry, did not help the sentiment around stocks in that sector.
Health-care shares were down slightly on Thursday with shares of insurer UnitedHealth leading the way, off by more than 1%. Some analysts have speculated that Bloomberg's success to date in the polls was easing fears that a populist Democrat will win in November. In pre-debate national polls, Bloomberg was in third place.
The blow to Bloomberg's odds came after he struggled to field questions about his record on race and policing as mayor as well as about allegations that he made crude remarks to women who worked for him.
The sharpest blows were delivered by Warren, who labeled Bloomberg a "billionaire who calls women 'fat broads' and 'horse-faced lesbians'" and demanded that he release his female employees from nondisclosure agreements immediately.
On the controversial "stop-and-frisk" policing policy that Bloomberg oversaw as mayor, the five other candidates on stage presented a united front, with Sanders saying it was "outrageous" and Biden rejecting Bloomberg's apology for the program as insufficient.
The criticisms were all previewed for days ahead of the debate, but Bloomberg failed to provide robust rejoinders. Bloomberg repeated an apology for stop-and-frisk, saying it was "the one thing I am really worried about, embarrassed about" from his time as mayor of New York City.
He declined to release his female employees from nondisclosure agreements or say how many such contracts there were.
"None of them accused me of doing anything other than — maybe they didn't like a joke I told," he said.
Rebecca Gill, a professor at the University of Nevada Las Vegas who researches politics and gender, said she was "gobsmacked" that Bloomberg did not have better answers to questions that he should have seen coming.
But, she said, his wealth may allow him to survive a devastating debate performance that might have been fatal for a candidate who was not a self-funded billionaire.
"He doesn't face the same problems that a normal candidate would face," Gill said. Bloomberg is the only candidate who does not accept campaign contributions. If he did rely on such donations, those might be drying up, Gill said, halting his staying power.
"I think that if we lived in a world that was post-racist and post-sexist, that performance should have been the end for him. But I don't know that it will be," she said.
Bloomberg is estimated to be worth more than $60 billion and has spent more than $400 million so far on campaign advertisements, making him a ubiquitous presence on television and online.
Despite that spending, GOP pollster Frank Luntz said on Thursday that the debate could potentially be the "beginning of the end."
"I don't think he captured the tone of the audience," Luntz said on CNBC's "Squawk Box."
The Bloomberg campaign sees it differently. Immediately after the debate ended, campaign officials told reporters that Bloomberg successfully drew a contrast with Sanders, who they said had not yet faced his own fair share of questions.
"You know you are a winner when you are drawing attacks from all the candidates. Everyone came to destroy Mike tonight," campaign manager Kevin Sheekey said in a statement.
In a demonstration of resilience, the campaign rolled out three new congressional endorsements on Thursday morning, including Rep. Nita Lowey, D-N.Y., the chair of the influential House Appropriations Committee.
— CNBC's John Melloy contributed to this report.