Of Michigan and Washington, in particular, Herman said, “They’re both daggers. They both cut arteries.”

The story on Tuesday was much as it has been since South Carolina, when Biden resurrected his campaign and coalesced moderate support. Sanders still has a following of young, progressive voters. But they are not turning out in sufficient numbers for him, and the Vermont senator is failing to broaden his base.

In Missouri, Sanders lost by fewer than 2,000 votes four years ago. On Tuesday, he lost the state so convincingly the contest was called almost immediately after polls closed. The losses continued in Michigan, where Sanders upset Hillary Clinton four years ago. And in Washington, where Sanders beat Clinton by more than 40 percentage points in 2016, the race was too close to call.

Following the Michigan outcome, Winnie Wong, a Sanders adviser, wrote on Twitter, “This race is not over. Let’s stay focused and work together.”

But the nearly insurmountable odds now confronting Sanders became obvious the minute the first states were called. Following Biden’s win in Mississippi, the primary crossed a threshold: Sanders would have to win more than 55 percent of delegates still on the board to secure a delegate majority.

That would be difficult under normal circumstances. But the landscape only gets more hostile to Sanders over the next two weeks. In Florida, the largest state voting next week, polls have Biden clobbering Sanders. Georgia, where Clinton drubbed Sanders four years ago — and where Biden is expected to do the same — holds its primary the following week.

Recognizing inevitability in the air, Andrew Yang, who supported Sanders in 2016 before running unsuccessfully himself for president this year, endorsed Biden on CNN on Tuesday night. Biden, he said, is “building a delegate lead that’s only going to grow in the days ahead.”

If Sanders has any hope left, it is a version of the one that sustained many of his competitors for much of last year: that Biden, gaffe-prone and woefully unsteady in his public appearances, might self-destruct. It is not impossible. Biden on Sunday will debate Sanders one on one for the first time.

But some progressives are nervous that Sanders won’t even make it that far.

Even before polling places closed on Tuesday, the Progressive Change Campaign Committee, which had supported Warren, appealed to Sanders to remain in the race “until the March 15th debate at the earliest,” seeking to avert what it called a “quick Biden coronation.”

Inside Sanders’ campaign, there are concerns that elected officials who have endorsed Sanders may begin to waiver, a source familiar with the campaign’s deliberations said. And outside of Sanders’ campaign, progressive Democrats are already shifting their horizons beyond their candidate.

‘The movement doesn’t go away after this week,” said Jeff Cohen, co-founder of RootsAction.org, an online activist group that supports Sanders. “It certainly doesn’t go away after the November election.”

Cohen said he is not “throwing in the towel yet.” But if Biden becomes the president — “and I sure hope that if he’s the nominee, he beats Trump,” Cohen said — “we will be, beginning the day after the election, organizing demonstrations against the Wall Street orientation of the administration.”

Sanders’ prospects of campaigning will now be limited by circumstances outside of his control. On Tuesday, both he and Biden were forced to cancel rallies because of the unfolding coronavirus outbreak. For a movement candidate who has made large rallies a signature of his campaign, the timing of the outbreak is significant.

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Now Sanders, who told ABC's "This Week" on Sunday that he is “not a masochist who wants to stay in a race that can’t be won,” will face enormous pressure to drop out.

He is not without leverage. Biden will need to win over the young people who support Sanders to defeat President Donald Trump in November, a calculation Biden tacitly acknowledged when he addressed them directly on Tuesday night.

Thanking Sanders and his supporters “for their tireless passion,” Biden said, “We share a common goal. And together, we’ll defeat Donald Trump.”

In addition to his supporters, Sanders possesses a massive fundraising list, what one Democratic National Committee member called “the gold mine.”

The committee member, a veteran of presidential campaigns, said that in exchange for his support, Sanders could negotiate with Biden for everything from speaking time at the Democratic National Convention to platform changes and appointments.

“He needs to sit down with [Tom] Perez or Joe’s people,” the DNC member said, referring to the DNC chairman.

Sanders can’t win, he said. “But he will be able to bargain.”

Scott Bland and Holly Otterbein contributed to this report.