Michael Bloomberg anticipated a hostile reception in his debut on the Democratic debate stage and his rivals didn't disappoint in Las Vegas on Wednesday evening, hammering him on issue after issue and leaving the billionaire struggling to respond to a string of expected questions.

Candidates also piled into national poll leader Bernie Sanders over the online abuse launched by some of his supporters, his electability and his healthcare plan. 

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In The Spotlight: Michael Bloomberg

Bloomberg was criticized on his attitude and behavior towards women, his record on criminal justice as mayor, his tax returns, his past support for Republicans and accused of hiding behind TV ads. 

The 78-year-old, who isn't competing in the upcoming Nevada caucuses, appeared uncertain and frequently eye-rolled on the highest profile political appearance of his career. His performance was so underwhelming that his campaign issued a statement after the debate saying he was "just warming up tonight."

Elizabeth Warren, who performed poorly in Iowa and New Hampshire, had a strong performance with repeated attacks on all the candidates on healthcare, hitting Sanders on electability but holding her fiercest criticism for Bloomberg.

"I'd like to talk about who we're running against," she started the debate by saying. "A billionaire who calls women fat broads and horse faced lesbians. And no, I'm not talking about Donald Trump, I'm talking about Mayor Bloomberg."

"Democrats are not going to win if we have a nominee who has a history of hiding his tax returns, of harassing women, and of supporting racist policies like red lining and stop and frisk. Look, I'll support whoever the Democratic nominee is, but understand this, Democrats take a huge risk if we just substitute one arrogant billionaire for another."

Pete Buttigieg, the former mayor who is leading the delegate count, engaged in fierce exchanges on the funding of Sanders' healthcare plan and also hit out at Bloomberg, starting the debate with a line likely to resonate with the party: "Let's put forward somebody who is actually a Democrat."

He called for a unity candidate and argued both Sanders and Bloomberg are polarizing, describing them as "a socialist who thinks that capitalism is the root of all evil and a billionaire who thinks money is the root of all power."

Bloomberg responded to criticisms from Sanders by dismissing his chances in a presidential election. "I don't think there's any chance of Senator Sanders beating Donald Trump," he said. "If he is the candidate, we will have Donald Trump for another four years and we can't stand that."

Joe Biden delivered a solid debate, Buttigieg and Klobuchar tussled with one another repeatedly, but the evening was dominated by the strong performance of Warren -- who spoke more than any other candidate, according to a New York Times tally -- and Bloomberg's terrible night. 

The billionaire, who has spent over 400 million U.S. dollars during his campaign so far, is far from knocked out but did take a major hit when put under pressure for the first time since entering the race.