The rapid consolidation of moderate Democrats behind Joe Biden after his win in the South Carolina primary created one of the quickest political reversals in history. On Saturday, Bernie Sanders was the favorite to win most of the states on Super Tuesday. Then came Biden’s strong victory in South Carolina and a rash of endorsements from rivals who had dropped out (Amy Klobuchar, Pete Buttigieg, Beto O’Rourke) plus party elders (former senator Harry Reid).

This outpouring of support revived Biden’s campaign. On Super Tuesday he won Alabama, Arkansas, Maine, Massachusetts, Minnesota, North Carolina, Oklahoma, Tennessee, and Virginia. Sanders won a smaller share of states: Colorado, Utah, and Vermont. California and Texas will still be counting for days to come, but it looks like Sanders won California, while Biden won a narrow victory in Texas. The overall results are likely to give Biden a 100-point delegate lead in the race.

It was a tough night for Bernie Sanders, who is clearly now the underdog. Biden’s campaign, which has struggled with fundraising, will now see money pouring in. Biden will be able to don not just the mantle of front-runner but also make a plausible case that he’s the unity candidate, since he’s won an impressive array of victories in diverse states while also winning over his former rivals. Now that Michael Bloomberg has also dropped out and endorsed him, Biden will get another boost, since he’s likely to pick up most of Bloomberg’s voters.

Still, the race is far from over, and Sanders’s victory in California and near-tie in Texas are evidence of a campaign that is much more diverse and dynamic than his 2016 run. But if the Sanders campaign is to narrow the gap, it’ll have to rethink some fundamental areas of strategy.

The Sanders campaign has been relying on a divided field and was blindsided by the snap-of-a-finger consolidation of the moderate candidates. To overcome this consolidation, the left needs to consolidate as well. The open question is what Elizabeth Warren will do. Sanders adviser Faiz Shakir told The New York Times, “We respect the fact that she’s going to make whatever decision she makes, and she should be allowed to do that.” He added that she “should be given the time and space” to decide her path. But if Warren does drop out and endorses Sanders, he’ll have an easier time consolidating the left.

Sanders will also have to recast his campaign, shunting aside themes like political revolution and focusing more narrowly on the electability question. Fortunately, there’s plenty to work with. Sanders is a more formidable debater than Biden, a contrast that will be visible if they appear on stage head to head. Further, Sanders can highlight Biden’s unpopular stances on cutting Social Security, as well as his support of the Iraq War. With the primaries in Michigan and Pennsylvania coming up, Sanders can also emphasize Biden’s support of NAFTA, unpopular with the working class of those states.

As Eric Levitz pointed out in New York magazine, Sanders’s posture as a political revolutionary has undercut his ability to appeal to party regulars. Levitz argues that “virtually all the polling we have on reliable Democratic primary voters suggests a large majority of them care much more about beating Donald Trump than winning an internecine fight for the soul of the Democratic Party in the name of socialism. And that polling also suggested that such Democrats were quite open to the idea that Sanders was their best bet for unifying the party and beating Trump.”

If Levitz is right, then Sanders’s best bet is to make the remainder of the contest about electability. To be sure, Biden would be able to respond with electability arguments of his own, based on Sanders’s self-identification as a socialist and past radical comments that sit uneasily with centrists. But the proper response to that is there is little evidence that voters care about those issues. By contrast, voters very much care about Social Security, about the endless wars in the Middle East, and about the free-trade agreements that ravaged the economy of the Midwest.

The other key electability argument is about the nature of Sanders’s coalition. Like no other candidate, Sanders attracts voters under 45. This is now the largest cohort of the electorate, but they have a much lower turnout rate than their elders. Sanders could plausibly argue that older partisan Democrats are likely to show up no matter who is on the ballot, as they did in 2016 and the 2018 midterms, because they hate Donald Trump. But younger voters are more marginal: They may or may not show up. So to maximize the Democratic coalition, the party needs to pick someone who excites the young.

The final thing Sanders needs to do is modulate the messaging on his own side so it is more issue-focused and avoids unnecessary attacks on moderate Democrats. On Tuesday night, Sanders supporter Marianne Williamson tweeted out, “This was not a resurrection; it was a coup. Russiagate was not a coup. Mueller was not a coup. Impeachment was not a coup. What happened yesterday was a coup. And we will push it back.” Williamson later deleted the tweet. This sort of intemperate and conspiratorial language undermines any possibility of Sanders presenting himself as a unifier.

Sanders is trailing. But he is still one of two contenders who have a chance to win the Democratic nomination. As such, he needs to present arguments that will convince those outside the fold that he is the one who can bring the party together.