In a punchy debate worthy of Las Vegas, billionaire Michael Bloomberg came under attack from all sides.

The field of candidates for the Democratic Party's presidential nomination has been shrinking for months, but on Wednesday night in Nevada, the debate stage had one significant new arrival.

For the first time since he launched his unconventional, money-suffused campaign in November, the former New York mayor directly faced off against his opponents.

And they nearly took his face off, rhetorically speaking. Here's how the two-hour fight for the right to challenge Republican President Donald Trump in November's election went down.

Right out of the starting gate, candidate after candidate took turns taking shots at the newcomer to the contest. It was the political equivalent of an incredibly lopsided tag-team wrestling match.

Bernie Sanders wasted no time highlighting the mayor's support of a stop-and-frisk New York City police policy that was heavily criticised by civil rights activists.

Elizabeth Warren brought up derogatory comments Bloomberg is reported to have made about women and the private agreements he has made to settle sexual harassment and hostile workplace lawsuits.

"Democrats take a huge risk if we just substitute one arrogant billionaire for another," she said, in an attempt to tie Bloomberg to Donald Trump.

Amy Klobuchar accused him of hiding behind his TV adverts, while Joe Biden highlighted his past criticism of Barack Obama's healthcare reform.

Meanwhile, Pete Buttigieg used one answer to go after both Bloomberg and Bernie Sanders, who it should not be forgotten is leading the national polls at the moment.