“[A]s the dust settles after March 3, the reality of this race will be clear: no candidate will likely have a path to the majority of delegates needed to win an outright claim to the Democratic nomination,” Lau predicted in a memo released Sunday. “In the road to the nomination, the Wisconsin primary is halftime, and the convention in Milwaukee is the final play.”

Biden’s dominant performance in South Carolina, however, could imperil that strategy if voters flock to him as the most viable alternative to Sanders. As results from the Nevada caucuses came in last weekend, Lau also predicted that Biden’s distant second-place finish was “further evidence of his steep decline.” Lau added on Twitter: “As we’ve said previously, further Biden collapse makes the race even more fluid.”

Instead, Biden won South Carolina by more than 28 points.

Still, the Warren campaign has long anticipated Biden would do well on Super Tuesday, with another memo earlier this month predicting he would be viable in 96 percent of districts.

After raising over $29 million in February, Warren probably can afford to let her strategy play out. The campaign has also gotten a major boost from a shadowy super PAC that has swooped in to provide over $14 million in air cover. Based on publicly available data, she has more resources than any candidate besides Sanders and Mike Bloomberg — certainly more than Biden, Buttigieg and Klobuchar.

History is stacked against a Warren comeback. No one has ever become the Democratic or Republican nominee in the modern primary era without coming in first or second in Iowa or New Hampshire (Biden and Klobuchar also fit in that category), let alone getting trounced in Nevada and South Carolina, too.

Warren’s campaign is often guarded about discussing internal strategy, but shifts in messaging have become apparent as she has campaigned across Nevada and South Carolina and in states voting on Super Tuesday.

She and her team have largely ditched her pitch about uniting the party and avoiding the intraparty factionalism of 2016 that made up much of her messaging in the weeks before Iowa and New Hampshire. That was part of a larger attempt to convince voters she was the most electable candidate.

Gone also are the television ads of former supporters of Sanders and Hillary Clinton talking about voting for Warren, which were part of her closing argument in the first two contests.

Warren has also been more willing to knock her rivals — especially Bloomberg, but also Sanders. The campaign began selling T-shirts with boxing gloves and "Nevertheless, she persisted" printed on them. After saying early last week she thought she’d make a better president than Sanders because she can actually get things done, she went further on Saturday night in Houston.

"This crisis demands more than a senator who has good ideas, but whose 30-year track record shows he consistently calls for things he fails to get done, and consistently opposes things he nevertheless fails to stop,” she said.

The comment upset some Sanders aides and supporters as the relationship between the two progressive allies and friends continues to deteriorate.

Warren has been particularly focused on casting herself as the more “effective” progressive. “If you think we need both progressive ideas and progressive results, then join us,” she said during the same speech, which she made as her dismal showing in South Carolina became apparent. During Tuesday's debate, Warren said: “We need a president who is going to dig in, do the hard work and actually get it done. Progressives have got one shot."

Warren's strategy ultimately relies on Sanders having a “ceiling,” as Lau recently argued, and on the scrutiny that comes with being a frontrunner causing some supporters to drift back to Warren.

Warren's allies have also been attempting to win back some support on the left that Sanders has consolidated by highlighting her prosecution of Bloomberg’s 24-karat candidacy. Some are hawking her as the “Bloomberg slayer.”

Warren’s team has also tested new arguments on electability after her unity-candidate messaging didn’t appear to work in the initial contests. The squishy concept of electability has dogged Warren more than her male rivals — in part because of many Democrats’ shock at watching Hillary Clinton lose in 2016, and in part because of double standards in American politics.

Two high-profile Warren surrogates — singer-songwriter John Legend and Jennifer Siebel Newsom, a filmmaker and actress who is the wife of California Gov. Gavin Newson — have told voters that it's impossible to know which candidate is the most electable. But Warren, they said, is a proven winner.

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“I know that Donald Trump is an existential threat to this nation and everyone is hoping and praying we pick the most electable candidate from the Democratic Party,” Legend said at a rally in Charleston, S.C., Wednesday night. “But the fact is, I can’t predict who the most electable nominee is. In 2016, we thought we did that. And you probably can’t predict who’s going to win either. So I’m voting based on who I think will make the best president.”

Siebel Newsom echoed a similar theme in her endorsement video . “Vote your conscience, not what the pundits and the billionaires are telling you to do,” she said. “Because Sen. Elizabeth Warren is electable.”

For her part, Warren has started off her events with a new rallying cry focused on electability. After Warren rarely mentioned the president in her stump speech most of the campaign, her new opening line goes: “My name is Elizabeth Warren. I’m the woman who’s going to beat Donald Trump.”

