Sanders’ campaign did not respond to a request for comment.

The salvo from Shumlin is the latest reaction to an ongoing spat between Sanders and Warren, two longtime friends who had taken part in a nonaggression pact before entering the 2020 presidential primary. But tensions have been building slowly between the two, coming to a head at Tuesday’s debate, when a hot mic caught Warren asking Sanders after the debate if he was calling her a liar on TV, after he denied saying in an earlier private conversation that a woman could not be elected president.

Shumlin, who also served two terms as DGA chair, slammed Sanders’ recent campaign tactics, reported by POLITICO, that cast Warren as elite. Sanders’ campaign briefly distributed talking points for supporters to use door-to-door, saying that Warren supporters “are highly-educated, more affluent people who are going to show up and vote Democratic no matter what” and that “she's bringing no new bases into the Democratic Party.”

And the day after Warren clashed with Sanders following a Democratic debate in Des Moines, #Warrenisasnake was among the hashtags trending on Twitter.

Shumlin accused Sanders of trying to “Hillarize” Warren, saying the senator had cast Hillary Clinton, too, as an elitist, contributing to divisions in the Democratic electorate.

“We should be weakening Donald Trump, not each other,” Shumlin said. “I’m concerned that we’re seeing a replay of the kind of dynamics that didn’t allow Hillary to win.”

Shumlin said his critique of Sanders is not sour grapes, noting that Sanders endorsed him and campaigned for him in Vermont. Shumlin also had attempted to enact a single-payer health care system in the state, an effort that ultimately failed.

Still, Shumlin teed off on Sanders’ relationship with Vermont Democrats.

“Don’t forget, the first office he won was beating the Democratic mayor of Burlington. He never endorsed most Democrats until his Senate career,” Shumlin said. “The only way he could win the Senate seat and avoid a Democrat winning the nomination and splitting the vote in the general election has been to run for the Democratic nomination, win it and immediately turn it down.”

In 2016, Sanders drew criticism for initially not campaigning for the Democratic nominee in the general election race in Vermont. He did later cut an ad for the candidate.

During the 2018 midterms, Sanders stumped for Democratic candidates across nine battleground states.