That latter breakthrough could be especially important for Biden in the upcoming midwestern states, where blue-collar white voters constitute a larger share of the Democratic primary electorate than in most places. A poll from Michigan released last night showed Biden pulling past Sanders there, even before the Super Tuesday results.

In 2016, Sanders won Michigan on the strength of a solid 15-point advantage among those working-class white voters. To keep them in his corner, he’s likely over the next week to stress his opposition to free-trade agreements that his rival supported, such as the now defunct North American Free Trade Agreement.

Read: Bernie Sanders meets his biggest threat

“Look at the states on March 10 and March 17,” said one senior Sanders adviser, who spoke on the condition of anonymity to discuss internal campaign planning. “We won Michigan because we hammered Clinton on trade. We are going to bring that back.”

But this time, Sanders could face pointed questions there, and in other states across the Rust Belt, about how his Green New Deal agenda could affect auto manufacturing, an issue that has received almost no attention in the race so far.

Perhaps the starkest symbol of Sanders’s limitations last night was the resurgence of a problem that severely damaged him in 2016: widespread resistance from primary voters who self-identify as Democrats (as opposed to independents).

In his 2016 race, exit polls found that Sanders won this bloc of voters only in New Hampshire and his home state of Vermont, and tied with Hillary Clinton among them in Wisconsin. Clinton beat him by about two to one among Democratic partisans in a cumulative analysis of all the exit polls conducted that year.

In the first stage of the 2020 race, Sanders seemed to have surmounted that problem: Among self-identified Democrats in Iowa, he finished just behind former South Bend, Indiana, Mayor Pete Buttigieg and about even with Biden and Warren. He also won a plurality of them in both New Hampshire and Nevada. But the issue resurfaced in South Carolina on Saturday, when Biden carried 54 percent of those voters, three times Sanders’s share.

The Super Tuesday exit polls showed Biden beating Sanders among self-identified Democrats by about 30 percentage points in both Virginia and North Carolina, about 25 points in Oklahoma, 20 points in Tennessee, and nearly 50 in Alabama. Sanders was more competitive among Democratic partisans in the New England states of Massachusetts and Maine. But the overall pattern was unmistakable.

His collapse among Democratic partisans came after recent full-throated attacks on “the Democratic establishment” in his rallies and media appearances. Sanders has often sounded more as if he believes he’s leading his movement in a hostile takeover of the party than a merger with it. (In his speech last night, he backed off only a half step, targeting his criticism at “the political establishment” rather than Democrats by name.) “It turns out that shitting all over the party you want to win the nomination of is a bad strategy,” said one Democratic pollster who is not affiliated with any campaign but requested anonymity to comment candidly on the race.