Sanders is running behind Biden by nearly 7 percentage points in Michigan, according to the latest Detroit News/WDIV-TV poll. But he is advertising heavily there and is adding stops to a weekend campaign swing. If he can hold Michigan and win Washington and Idaho on Tuesday, he could shift momentum back in his favor.

“It all hinges on next Tuesday,” said Mark Longabaugh, a senior adviser to Sanders' 2016 presidential campaign. “If Bernie wins three out of the five next week — especially Michigan and Washington state … the narrative’s going to be, ‘Bernie’s back.”

He said, “If Bernie can win Tuesday, this is going a long way.”

It is Biden who, in many ways, is the unlikely participant in this two-person race. Unlike Clinton, who won two of the first three early states, the former vice president had come close to bottom before ascending. Before South Carolina, the three-time presidential contender had never won a state. He had little organization and had nearly run out of money.

“The shocking thing on Super Tuesday is that Biden won all these states [where] he had no resources on the ground, no field operations to speak of anywhere,” said Terry McAuliffe, the former Virginia governor and former Democratic National Committee chair, who endorsed Biden after his victory in South Carolina. “We’ve never seen this in the history of American politics.”

But McAuliffe, who reviewed Biden’s polling with African American voters, among other constituencies, before deciding himself not to run, said he predicted more than a year ago that Biden was “pretty insurmountable.”

In 2016, Clinton proved insurmountable in the primary, too. And there was one significant difference between her and Biden: He does not share her high unfavorable ratings.

Still Biden, like Clinton, is taking a bruising from the left. Sanders this week began airing an ad featuring a union autoworker lauding Sanders for his opposition to trade deals and criticizing Biden for his support for them. He used a similar argument against Clinton, right down to the language in his ads.

“Joe is going to have to explain to the people, the union workers in the Midwest, why he’s supported disastrous trade agreements,” Sanders said at a press conference in Vermont a day after Super Tuesday. “Joe is going to have to explain to the American people why he voted for a Wall Street bailout, something that I vigorously opposed.”

The news conference — in its timing and its content — was similar to the hours after Super Tuesday in 2016, when Clinton’s victories pushed Sanders to the brink. Sanders, noting at the time that 35 states had yet to vote, said “we are going to take our fight for economic justice, for social justice, for environmental sanity, for a world of peace to every one of those states.”

Sanders is signaling a similar effort this year, and he has the fundraising to do it. He is also frightening moderate Democrats, as he did then.

“Biden is following a very similar trajectory to Hillary, which was that Iowa and New Hampshire and Nevada, frankly, are just massively exotic contests that are not at all really representative of America,” one Democratic strategist said. “They’re ideological, left wing, and you have to muddle through them. And then you start winning in South Carolina and Super Tuesday. And Biden had to follow that same path.”

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He said, “The question going forward is does Bernie choose to basically impugn Biden’s character as a means of pulling ahead.”

On Thursday, the day Elizabeth Warren abandoned her campaign — removing the last credible alternative to Biden and Sanders — Ed Bruley, the chairman of the Democratic Party in Michigan’s Macomb County, said either Biden or Sanders could beat Trump.

But Bruley, who supported Warren and whose famed swing county in the Detroit suburbs voted twice for Barack Obama before flipping to Trump, said, “They need to lower the rhetoric. When you had nine people … the little differences between each of them, it wasn’t as pronounced.”

Now, he said, “We have to be careful.”

“The drama that we’re going through now is an internal family drama, and I don’t think that it is really helpful to what we need to be ready for in November,” he said.

Besides the negatives surrounding Clinton, the Democratic Party’s view of what is coming in November is the other major difference from 2016. Whereas few people took Trump seriously at this time four years ago, concerns about how to defeat Trump framed the Democrats’ entire nominating contest this year.

On Tuesday night, Paul Maslin, a top Democratic pollster who worked on the presidential campaigns of Jimmy Carter and Howard Dean, was trying to make sense of how the party found itself in a Groundhog Day situation, going back to the botched Iowa caucuses.

“Stations at a cross. Iowa f--- up. State of Union. Impeachment. New Hampshire. Debate. Nevada. Bernie goes on 60 Minutes and talks Castro. Debate. Clyburn. Biden blowout. Endorsement Sunday. Joementum," he wrote at the end of a lengthy text message. "No one has guts tonight to say this is done. But it is. Now it’s a Trump sleepy Joe world for the better part of seven months once Bernie is beaten. Who would have thunk this?”