Senator Bernie Sanders faced a torrent of attacks from his Democratic rivals today during a high-stakes debate that could be their final prime-time opportunity to change the direction of the 2020 nomination fight.
Businessman Mike Bloomberg seized on reports that Russia was interfering in the 2020 presidential election to help Sanders.
Former Vice-President Joe Biden attacked Sanders for considering launching a primary challenge against former President Barack Obama.
And even Sanders' ideological ally, Senator Elizabeth Warren, said she'd be a better president than the Vermont senator.
Sanders, who has risen to be the Democrats' clear frontrunner, responded: "I'm hearing my name mentioned a little bit tonight. I wonder why?"
The new wave of infighting came as Democrats met for the party's 10th — and perhaps most consequential — debate of the 2020 primary season. Today's forum came just four days before South Carolina's first-in-the-South primary and one week before more than a dozen states vote on Super Tuesday.
The intensity of the clash, with candidates repeatedly yelling over each other, reflected the reality that the Democrats' establishment wing is quickly running out of time to stop the polarising progressive.
Bloomberg was the focus last week for his highly anticipated debut, but after a bad performance that froze his momentum, the knives were out for the 78-year-old Vermont senator.
Bloomberg made the case that both Trump and Russia President Vladimir Putin are in lockstep in their belief that Sanders would make the weakest Democratic general election rival for the incumbent Trump. Last week, Sanders acknowledged that he'd be been briefed by intelligence officials who said that Russia is attempting to interfere in the elections to benefit him.
"Vladimir Trump thinks Donald Trump should be president of the United States and that's why Russia is helping you get, so you lose to him," Bloomberg said.
Sanders shot back, "Hey, Mr Putin, if I'm president of the United States, trust me you're not going to interfere in any more American elections.'"
Biden was also looking to make a big impression in South Carolina, where he was long viewed as the unquestioned front-runner because of his support from black voters.
Biden slammed Sanders for his support of the 2005 Protection of Lawful Commerce in Arms Act, legislation that protects gun manufacturers and sellers from laws that attempt to hold them liable for dealing firearms that end up in the hand of criminals.
"My friend to my right, and others, have in fact also given in to gun manufacturers absolute immunity," said Biden, referring to Sanders backing of the controversial gun legislation. "Imagine if I stood here and said, 'We give immunity to drug companies. We give immunity to tobacco companies.' That has caused carnage on our streets. "
Sanders proudly highlighted his "D minus" rating from the pro-gun organisation. And just last week, several gun control advocates who survived the Parkland, Florida, school shooting endorsed him.
Warren had resisted attacking Sanders, her ideological ally, for much of the last year. Today, the Massachusetts senator trained her focus on both Sanders and Bloomberg, whom she savaged last week on the debate stage.
In her most direct shot at Sanders, Warren made the case she's simply the better candidate.
"Bernie and I agree on a lot of things, but I think I would make a better president than Bernie," Warren said. "And the reason for that is that getting a progressive agenda is going to be really hard, and it's going to take someone digs into the details to make it happen."
Yet Warren saved her fiercest attacks for Bloomberg.
She cut hard at Bloomberg's record as a businessman, bringing up reports of one particular allegation that he told a pregnant employee "to kill it," a reference to the woman's unborn child. Bloomberg fiercely denied the allegation, but acknowledged he sometimes made comments that were inappropriate.
Bloomberg "cannot earn the trust of the core of the Democratic Party," Warren said. "He is the riskiest candidate standing on this stage."
Former mayor Pete Buttigieg says the cost of Sanders' healthcare plan "adds up to four more years of Donald Trump."
He also says it would make California Republican Kevin McCarthy the speaker of the House and stop Democrats from winning back control of the US Senate.
Buttigieg echoed Democrats who have warned that a Sanders nomination would harm candidates running in down-ticket races. Buttigieg says Democratic candidates who flipped House seats in 2018 don't want to defend Sanders' policies on "Medicare for All."
He said, "The time has come for us to stop acting like the presidency is the only office that matters."