They tried to keep smiling, but it was gloves off for the six Democratic candidates during Wednesday night’s debate in Las Vegas.

Unlike the previous eight debates, this time was a bare-knuckles brawl suitable for a city known almost as much for championship boxing as for its ubiquitous slot machines.

Not that there were any actual fisticuffs, but “heated” is an understatement for the debate, held to a strict two hours by NBC News.

Onstage were Sens. Bernie Sanders (I-VT), Elizabeth Warren, (D-MA) and Amy Klobuchar (D-MN); former South Bend, Indiana mayor Pete Buttigieg; former vice president Joe Biden; and, in his first debate of the campaign, late entry Mike Bloomberg.

As expected, Bloomberg took loads of verbal abuse from his rivals.

Sanders, who came into the event with a substantial lead in national and Nevada polls, became a secondary target for the other four contenders.

Bloomberg, the billionaire former mayor of New York City and an inexperienced debater, “struggled from the start to address his past support for stop-and-frisk policing and the allegations he has faced over the years of crude and disrespectful behavior toward women,” reports the New York Times.

“Time and again, Mr. Bloomberg had obvious difficulty countering criticism that could threaten him in a Democratic Party that counts women and African-Americans among its most important constituencies,” the Times said.

On stop-and-frisk, Bloomberg admitted he let it go too far by targeting black and Latino neighborhoods: “The bottom line is that we stopped too many people,” he said.

But when Sanders declared that billionaires shouldn’t even exist in America, Bloomberg bristled:

“I can’t think of a way that would make it easier for Donald Trump to get reelected than listening to this conversation,” he said. “It’s ridiculous. We’re not going to throw out capitalism. We tried that. Other countries tried. That was called communism, and it just didn’t work.”

Sanders, a dedicated progressive independent who works with the Democrats in Congress, bristled right back, with a grimace and a shake of the head that showed his contempt for Bloomberg’s use of the word “communist.”

Warren, who has often clashed with her fellow progressive Sanders, did him a “massive favor by taking a chain-saw to Bloomberg,” the Washington Post says, by noting his previous derogatory words about women — “fat broads” and “horse-faced lesbians” — words many Americans might attribute to Trump, but were in fact spoken by Bloomberg, years ago.

“We are not going to beat Donald Trump with a man who has who-knows-how-many nondisclosure agreements and the drip, drip, drip of stories of women saying they have been harassed and discriminated against,” Warren said.

“Democrats take a huge risk if we just substitute one arrogant billionaire for another,” she added.

Klobuchar, who has intrigued many with her canny performances in earlier debates, failed to ignite much of a fire this time, even thrown off-guard by an long-ago flub in which she failed to recall the name of Mexico’s president.

“She name-checked ‘President López Obrador’ in the answer, but she struggled to pronounce his name correctly. Then she tried to recite other trivia about foreign leaders but stumbled, appeared to check her notes, and mustered only a last name for another Latin American president,” the Post says.

Buttigieg took on both Bloomberg and Sanders, calling them the “most polarizing figures” on the stage.

“Let’s put forward somebody who’s actually a Democrat,” Buttigieg said, a reference to Sanders, who styles himself an Independent Socialist, and Bloomberg, an enormously wealthy former Republican.

Biden had clearly worked hard preparing for this debate, and he made no notable gaffes. But his campaign is unlikely to have gained any ground from his performance Wednesday.

“If there was a bystander on the debate stage Tuesday night, it was Biden,” the Post says. “There was nothing there to suggest he might rescue his struggling campaign.”

Returning to Sanders, early in the debate his rivals homed in on the so-called “Bernie bros” and their “nastiness” online toward the other Democratic candidates, the Post says.

“Why is [this] especially the case among your supporters?” Buttigieg asked.

“I don’t think it is actually the case,” Sanders said. “That’s just not true.”

Most political journalists would disagree. They say it’s a major issue with the Bernie bros, compared with supporters of other candidates — and Sanders’ retort suggests he isn’t taking it seriously.