On Super Tuesday, Senator Bernie Sanders delivered an angry denunciation of his rival Joe Biden to supporters in Colorado.

So we’re going to beat Trump because this will become a contrast in ideas. One of us in this race led the opposition to the war in Iraq; you’re looking at him. Another candidate voted for the war in Iraq. One of us has spent his entire life fighting against cuts in Social Security and wanting to expand Social Security. Another candidate has been on the floor of the Senate calling for cuts to Social Security, Medicare, Medicaid, and veterans. One of us led the opposition to disastrous trade agreements, which cost us millions of good-paying jobs. And that’s me. And another candidate voted for disastrous trade agreements. One of us stood up for consumers and said, “We will not support a disastrous bankruptcy bill.” And another candidate represented the credit-card companies and voted for that disastrous bill.

The speech departed from Sanders’s 2020 preference for speaking positively about his own message, and reverted to Sanders’s 2016 practice of bitter attacks on his main opponent. John Cassidy reported one of those speeches in April 2016, for The New Yorker:

When he brought up Hillary Clinton’s paid speeches to Wall Street companies, loud boos echoed across the park. He also took Clinton to task for supporting free-trade agreements, which he said had cost America many well-paying jobs; for consorting with Henry Kissinger; and for having a super PAC that has raised tens of millions of dollars from special interests. But he saved his harshest vitriol for Verizon, Big Pharma, the Koch Brothers, the Walton family (the founders of Walmart), and, of course, Wall Street. “This campaign is sending a message to corporate America: you cannot have it all!” he said. Sanders did dress up some of his applause lines for his audience. For months, he has been saying that Clinton’s speeches for Goldman Sachs must have been corkers to have merited fees of more than two hundred thousand dollars each. Now he added, “It must be a speech that could solve most of the world’s problems. It must be a speech written in Shakespearean prose.”

This time, as a would-be front-runner (and in the two weeks from the New Hampshire primary to South Carolina, the actual front-runner), Sanders modulated his tone about the party he aspired to lead. Cast back into second-place status, Sanders has returned to his old rhetoric of accusation.

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Sanders did soften his tone somewhat the day after. “I like Joe,” the senator said on Wednesday. “I think he’s a very decent human being.” But with that caveat, Sanders resumed the personal attack:

Joe and I have a very different voting record. Joe and I have a very different vision for the future of this country. Joe and I are running very different campaigns … Joe is running a campaign which is obviously heavily supported by the corporate establishment … What does it mean when you have a campaign which is funded very significantly by the wealthy and the powerful? Does anyone seriously believe that a president backed by the corporate world is going to bring about the changes that the working class and middle-income people desperately need?

The immediate function of these words is to energize Sanders’s faltering primary campaign. As Sanders has often stressed, his campaign regards both President Donald Trump and the existing Democratic Party as adversaries. Trump may be just slightly worse from the perspective of Sanders and his allies, but their hostility to the Democratic Party is more intimate and immediate. “It’s Armageddon time for the Democratic Party,” Sanders supporter Ralph Nader said in an interview with The Intercept in mid-February. Nader envisioned a huge surge of left-wing pro-Sanders votes that would not only defeat President Trump, but that “will sweep out the corporate Democrats in the Democratic National Committee, and it will reorient the Democratic Party to where it should be, which is a party of, by, and for the people. That’s why they want to fight him.”