Liberal Democrats are desperately trying to stay united amid a dispute between Sens. Bernie Sanders Bernie SandersKenosha will be a good bellwether in 2020 Biden's fiscal program: What is the likely market impact? McConnell accuses Democrats of sowing division by 'downplaying progress' on election security MORE (I-Vt.) and Elizabeth Warren Elizabeth WarrenBiden's fiscal program: What is the likely market impact? Warren, Schumer introduce plan for next president to cancel ,000 in student debt The Hill's 12:30 Report - Presented by Facebook - Don't expect a government check anytime soon MORE (D-Mass.), which has raised fears on the left that they’ll fumble a prime opportunity to nominate a candidate from the progressive wing of the party.

Many on the left had hoped to see the progressive standard-bearers move past a bitter conflict over whether Sanders told Warren at a private meeting in 2018 that a woman could not be elected to the White House.

Instead, the divisions between them appeared to deepen following Tuesday night’s debate, underscored by an unpleasant post-debate exchange caught on video that found them walking away from one another without shaking hands. CNN released audio of the exchange late Wednesday, revealing that Warren accused Sanders of calling her a "liar on national TV."

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Views of the Sanders-Warren battle are hardening fast and tensions are running hot as supporters for each candidate retreat to their corners to accuse the other side of playing dirty.

It’s a high-stakes affair that risks damaging both candidates, who are running at the top of many polls in Iowa with the caucuses only weeks away.

Liberals are worried that continuing down this path will dampen enthusiasm for the progressive left’s brightest lights and make it more likely that a centrist candidate, such as former Vice President Joe Biden Joe BidenSenate Republicans face tough decision on replacing Ginsburg What Senate Republicans have said about election-year Supreme Court vacancies Biden says Ginsburg successor should be picked by candidate who wins on Nov. 3 MORE or former South Bend, Ind., Mayor Pete Buttigieg Pete ButtigiegBipartisan praise pours in after Ginsburg's death Bogeymen of the far left deserve a place in any Biden administration Overnight Defense: Woodward book causes new firestorm | Book says Trump lashed out at generals, told Woodward about secret weapons system | US withdrawing thousands of troops from Iraq MORE, will emerge victorious.

“When progressives are fighting, the corporate wing will try to use it as a way to divide us,” said Neil Sroka, a strategist for the progressive group Democracy for America. “We’re fully conscious that the quest for the nomination is a zero-sum game and that individual voters will have to make a choice between these candidates. But we have to make sure the battle between the progressives doesn’t get so ferocious that it allows the corporate wing of the party that doesn’t have the same passion around it to slip in and win.”

Supporters of both candidates walked away from Tuesday night’s debate feeling emotionally drained, disappointed and ready to scrap.

Sanders allies feel betrayed by what they view as a low blow over an old misunderstanding.

“I felt a knife in the heart,” said Michael Moore, a liberal activist and filmmaker who backs Sanders.

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Sanders’s allies are furious at debate host CNN for fanning the flames and for framing questions about the dispute in a way that appeared to take Warren’s side, undercutting and embarrassing the Vermont senator.

And they’re angry at Warren’s effort to cast herself as the most electable candidate by claiming to have been the only person on stage to defeat an incumbent Republican in the past 30 years, a moment that led to an awkward debate exchange with Sanders when he seemingly tried to correct her.

“Thirty years ago, she was a Republican,” said Nina Turner, a co-chairwoman for Sanders’s campaign.

Sanders’s supporters said the tiff had grown into something worse than they could have possibly imagined.

“This isn’t great,” one Sanders ally said. “They really need each other if progressives hope to win. I’m disappointed by the turn of events, and that’s an understatement.”

Sanders has clear momentum in the stretch run to Iowa, but the allegation from Warren is potentially damaging for his campaign because it draws attention to several controversies.

Sanders has been criticized for not doing enough to support former Secretary of State Hillary Clinton Hillary Diane Rodham ClintonWhat Senate Republicans have said about election-year Supreme Court vacancies Bipartisan praise pours in after Ginsburg's death Trump carries on with rally, unaware of Ginsburg's death MORE’s general election bid in 2016, when she narrowly lost to President Trump Donald John TrumpObama calls on Senate not to fill Ginsburg's vacancy until after election Planned Parenthood: 'The fate of our rights' depends on Ginsburg replacement Progressive group to spend M in ad campaign on Supreme Court vacancy MORE.

And Sanders apologized last year after several campaign aides were accused of harassing women. His online supporters — the so-called Bernie Bros — have been accused of sexist attacks against rivals, critics and reporters.

Still, the controversy with Warren rallied Sanders’s supporters around him.

They were enthused that Sanders recounted how he had asked Warren to run for president before he got into the race in 2016. Supporters shared videos of past remarks in which Sanders talked about how he believes a woman can be elected president. The hashtag “Women for Bernie” trended on Twitter and the campaign said it raised an astonishing $1.7 million in the hours after the debate.

Warren’s supporters have matched that intensity of support and are furious that Sanders would challenge her view of their conversation, arguing that women should be believed when they say they’ve been mistreated or dealt with in a condescending manner by powerful men.

Warren electrified the room at Tuesday’s debate when she pivoted off the allegation to make the case for nominating and electing more women in politics.

“Look at the men on this stage,” Warren said. “Collectively, they have lost 10 elections. The only people on this stage who have won every single election that they’ve been in are the women: [Sen.] Amy [Klobuchar (D-Minn.)] and me.”

But there are enormous risks for Warren, who cannot afford to alienate Sanders’s liberal coalition. Warren has sought to cast herself as a unity candidate who can bridge the gulf between the progressive left and the moderate center.

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Behind the scenes, progressive groups were working quickly to try to unite the two sides, according to sources.

“We need to be on the same team,” one Democratic operative said. “This isn’t good.”

Other progressives said the fight is being overblown and that the centrist candidates are just as busy tearing one another down.

“Biden is potentially going to lose the first three states because Buttigieg and Klobuchar are siphoning off his votes, but there’s a viral moment between Sanders and Warren so I guess no one cares,” said one progressive strategist.

Democratic strategist Eddie Vale said it’s better for both campaigns to move on.

“It’s not in either of their short-term interests to have this issue continue now through Iowa,” Vale said. “She wants to pivot to her broader message like she did last night. He wants to be arguing foreign policy, [the] economy ... with Biden.”

Democratic strategist Christy Setzer added that “it’s only bad if one camp chooses to take this tiff as a reason to write off the other candidate, even in the face of a Trump reelection.”

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“The concern is that Team Sanders may be prone to a ‘Bernie or bust’ mentality and that Warren just gave them ammunition for their ‘or bust,’ ” Setzer said. “Hopefully not.”

There are some early signs of repair.

“Forget those who are trying to divide us, focus on building the progressive movement and be positive to succeed,” tweeted Jane O’Meara Sanders, Bernie Sanders’s wife.

And Maria Langholz, a strategist at the Progressive Change Campaign Committee, which backs Warren for president, tweeted: “I love Warren, obviously. Bernie would be a great president too.”