Democratic presidential candidate, former New York City Mayor Michael Bloomberg speaks about affordable housing during a campaign event where he received an endorsement from District of Columbia Mayor Muriel Bowser on Thursday in Washington DC. Photo: AFP

 

Former New York mayor Michael Bloomberg endured a punishing assault in his debut Democratic presidential debate on Wednesday from rivals who savaged him for parachuting in late and throwing astronomical amounts of money at the race.

The Las Vegas showdown came at a tense time in the party's nomination race, with leftist firebrand Bernie Sanders coalescing as the frontrunner and some challengers fighting for survival.

US media magnate Bloomberg found himself targeted from the start, as candidates from Sanders to former vice president Joe Biden impugned the man whose sudden prominence in polling has scrambled the race to defeat President Donald Trump.

"Understand this: Democrats take a huge risk if we just substitute one arrogant billionaire for another," Senator Elizabeth Warren said in a fiery attack on 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," she added.

Sanders hit Bloomberg hard on his vast wealth at a time of "grotesque" income inequality in America.

"Mike Bloomberg owns more wealth than the bottom 125 million Americans," Sanders said in one of the night's many abrasive moments. 

All eyes were on Bloomberg's first appearance on the debate stage after spending hundreds of millions of dollars on campaign advertising.

He endured a very public vetting and struggled to highlight his roles as problem solver, businessman, city manager and philanthropist.

He found himself on the defensive when pressed to explain sexual harassment claims against him and employees, his delay in releasing his taxes and more.

Bloomberg at one point managed to push back forcefully against Sanders, saying if the self-declared democratic socialist is the nominee, "we will have Donald Trump for another four years."

Establishment Democrats have begun public hand-wringing about the prospects of Sanders taking the reins of a party seeking to make Trump a one-term president.