Just a few weeks ago, the Democratic primary—and the state of the country—looked completely different. Bernie Sanders had claimed victory in the first three contests and seemed to be running away with the nomination. Joe Biden, by contrast, was perhaps one more disappointing finish away from being knocked out of the race he’d led in national polls since entering it. But now, after racking up primary victories across the country, including some in decisive fashion, Biden has built a commanding delegate lead, is easily outpacing Sanders in national polls, and has forced his progressive rival to consider the future of his campaign.

Sanders was recently sending signals that he had no intention of leaving the race just yet. “I want the senator to stay in,” Nina Turner, one of the national co-chairs of his campaign, said earlier this week. But after another drubbing Tuesday in which Biden swept three more states, there are signs that Sanders may be preparing to exit. After losing Arizona, Florida, and Illinois on Tuesday, Sanders suspended Facebook advertisements, fueling speculation that his once-promising run was drawing to an end. An email to supporters updating them on the state of play which did not include the typical request for donations kept the rumor-mill churning. And while Axios pulled back its Wednesday report that Sanders was suspending his campaign, the Washington Post reported later that his campaign has been in regular contact with Biden’s team, apparently to discuss policy ideas about the novel coronavirus that has upended American life—a sign, potentially, that Sanders could soon step aside and cement Biden as the party nominee to take on Donald Trump in November.

“Bernie is the person—the one person—who can essentially give the Biden campaign permission to start the general election, to start talking to the [Democratic National Committee], to start building the general election operation we need,” Rufus Gifford, a top Biden fundraiser, told the Post. “That’s why it matters sooner rather than later.”

As Biden’s momentum has grown, a chorus of voices have called for Sanders to drop out and unify the party against Trump. “The stakes are so high,” former Labor secretary Robert Reich, a Sanders supporter, told the New York Times earlier this week. But the senator has seemed resistant, despite more or less needing to win the remaining primaries in routs to claim a majority—an even less favorable position, as FiveThirtyEight’s Nate Silver pointed out Wednesday, than he found himself in at this stage of the race against Hillary Clinton in 2016. “This is a steeper climb,” Silver tweeted.

Further compounding Sanders’ position is the coronavirus crisis, which has cast doubt on the ability of states to safely hold elections, forced the nation’s attention away from the primary race, and reinforced the need among Democrats to defeat Trump at all costs, thanks to his mishandling of the pandemic. “This campaign’s over. He needs to acknowledge that and be gracious about it,” Matt Bennett, co-founder of the center-left think tank Third Way, told Politico. “Not only for party unity, which is up to him, but just for the sake of humanity, it would be better for him to wrap this up.”

The only other remaining Democratic candidate, Rep. Tulsi Gabbard, announced Thursday she was formally leaving the race and offering her “full support” to Biden “in his quest to bring our country together." The Biden campaign appears to be giving Sanders his space, with campaign officials now following an internal policy to no longer attack the Vermont senator. But with the math stacked against him, and the stakes in November high, the pressure will nevertheless continue to grow for him to bring the party together and avoid the internal divides that hurt the Democrats in 2016. “I think there’s every reason in the world for Bernie to assess and get out,” Representative Don Beyer, a Biden supporter, told the Post. “I definitely think it is” irresponsible for Sanders to remain in the race.”