Bernie Sanders’ campaign recently stabbed Elizabeth Warren in the back. She was the Vermont senator’s comrade in arms. It also threw a pack of lies at Joe Biden, tarring him as corrupt with zero evidence. As former Vermont Gov. Peter Shumlin told Politico, Sanders “will play dirty.” The Democrat added, “I’m concerned that we’re seeing a replay of the kind of dynamics that didn’t allow Hillary to win.”

The difference between now and 2016, though, is that Sanders’ targets are finally hitting back. This outbreak of hostilities among Democrats is not hurting the party. On the contrary. An airing of these grievances is long overdue.

And whether one shares Sanders’ political views is irrelevant to this conversation.

The danger Sanders poses for the party is that, to him, electing Democrats comes second to building the “movement.” This explains why his sidekick, Rep. Alexandria Ocasio-Cortez, is pushing primary challenges to moderate Democrats who won difficult races in swing districts.

The catchphrase on Sanders’ website, Our Revolution, is “Campaigns end. Revolutions Endure.” Indeed, he and his fellow socialists have latched on to the Democratic Party because having a D after their names is the only way they can win an election.

Few things make the Bernie base madder than the charge that their hero helped sabotage Clinton’s candidacy. Its members passionately note that he politicked for her in the last days of the campaign. That’s true, but by then, not doing so was tantamount to openly supporting Donald Trump.

Early in 2016, when it seemed possible that Sanders might score more votes than Clinton, he assailed the superdelegates who mostly backed Clinton and could have delivered her victory. His supporters demanded that superdelegates reflect the popular vote, “not the party elites.”

By June, when Clinton had racked up a commanding majority of primary votes, Sanders did an about face and urged the superdelegates to ignore the voters and support him. “Superdelegates have a very important decision to make,” he told NBC News.

Upon winning the Republican nomination, Trump announced, “To all of those Bernie Sanders voters who have been left out in the cold by a rigged system of superdelegates, we welcome you with open arms.”

Trump was the official Republican candidate, and Sanders still wouldn’t back the Democratic one. In the weeks leading up to the Democratic National Convention, he withheld his endorsement of Clinton, insisting that certain demands be met. Some of his delegates chanted “Lock her up!” right on the convention floor.

Some of his supporters are now spreading the fear that history could repeat itself if a moderate such as Biden becomes the nominee.

Elaine Godfrey wrote in The Atlantic that progressive organizers she has spoken with said they are “worried that, absent a Democratic candidate who excites them, many Americans might not vote at all.”

Trump should excite them enough. People who don’t get that they are voting against as well as for are political neuters. Are they going to help re-elect Trump on Tuesday and then rage on Wednesday that he’s burning up the planet?

Yes, mainstream Democrats had to have it out with the heretic hunters of the left. The person most displeased by this counterattack on Sanders surely must be Trump. Sanders is the candidate Trump most wants to run against. And that should tell Democrats something.

Froma Harrop is a syndicated columnist.