As Bernie Sanders’s decisive primary defeats Tuesday put him almost hopelessly behind in the race for the Democratic nomination, he began facing growing calls to withdraw from Democrats who want the party to unite and focus its energy on defeating President Trump.

Even before Tuesday’s big losses in Florida, Illinois and Arizona, a chorus of Democrats was publicly urging Sanders to drop out. With upcoming primaries likely to be postponed due to the coronavirus pandemic, Democrats increasingly worry that former vice president Joe Biden, who leads the race by a comfortable margin, might not be able to fully turn his focus to Trump before late summer if Sanders stays in.

“After tonight, with no path to secure the nomination, @BernieSanders should drop out,” Bakari Sellers, a former South Carolina state lawmaker who initially endorsed Sen. Kamala D. Harris (D-Calif.), tweeted Tuesday night. “We should proceed to the mission at hand, beating Trump.”

Former senator Claire McCaskill (D-Mo.) made a similar point. “I think the conversation is going to quickly turn to how and when does Bernie Sanders unite the Democratic Party,” McCaskill said on MSNBC. “I do think the pressure is going to mount, especially at this time of crisis in this country, for the Democrats to unite behind clearly the voters’ preference.”

Yet some Sanders supporters argue vociferously that he should stay in precisely because of the public health crisis, which they say underlines his messages on universal health care and income inequality, creating intense cross-pressures and an especially difficult dilemma for a candidate who has built a loyal liberal movement.

Sanders and his wife, Jane, are expected to reach a decision together about the future of the campaign, people in frequent contact with them said, taking input from advisers but making the call on their own. Many Democrats are waiting anxiously to see what Sanders says on Wednesday about the future of the race, if anything.

Sanders spent Tuesday in Washington, where the Senate was hashing out legislation to combat the vast impact of the virus. Jane Sanders traveled to Washington with him, according to a campaign official with knowledge of the situation.

In an address from Washington live-streamed online Tuesday night, Sanders made no mention of the primaries or the future of his campaign, instead focusing exclusively on the coronavirus crisis. He outlined proposals to address the pandemic, including empowering Medicare to cover all medical bills during the crisis.

“I look forward to continuing to communicate with you to tell you where we are coming from, what our ideas are, and look forward to hearing from you,” said Sanders, signaling an intent to stay involved in the political conversation.

Biden extended an invitation to Sanders voters Tuesday, praising them and saying “they have shifted the fundamental conversation in this country.” He added, “Let me say especially to the younger voters who have been inspired by Senator Sanders: I hear you.”

But it was unclear those entreaties would work. RoseAnn DeMoro, a close friend of Sanders and the former head of an influential nurses union, said earlier Tuesday that the current social and political volatility is alone justification for Sanders to stick it out. “Anything can happen within the next several months, and he would be forfeiting his delegates if he got out,” DeMoro said.

After opting for a middle ground last week — neither exiting the race nor signaling it was full speed ahead — the senator from Vermont found his back against the wall once again Tuesday.

The rapidly escalating coronavirus crisis has forced Biden and Sanders to cancel rallies and other activities indefinitely. Before the widespread recognition of the pandemic’s seriousness, several Sanders allies expected him to closely consider dropping out if Tuesday’s results were disappointing, but the current landscape is throwing the usual calculations into question.

Larry Cohen, who heads a pro-Sanders nonprofit organization, said earlier this week that he thinks Sanders ought to remain in the race and accrue delegates to the Democratic National Convention, so he can maintain his leverage with the Biden forces when it comes to forming committees and shaping the party’s approach to health care and climate change.

“That’s the way the party gets built,” said Cohen.

Inside the Sanders campaign, a similar perspective could be found. Nina Turner, a national co-chair and one of Sanders’s most trusted advisers, said Monday that “there are millions of people who are depending on him” to promote his calls for a universal health-care system and other sweeping liberal programs.

At the same time, mounting concerns about the virus and the safety of voting have come into consideration, raising new questions about the merits of pushing ahead in a race that appears increasingly unlikely to result in victory. Pressure from Democrats to unify against a president they revile has been intensified by the sense of national crisis, which could make running a doomed race seem less appropriate.

The Sanders campaign has sent mixed signals in recent days on whether it considers it safe for voters to participate in the primaries. Sanders spokesman Mike Casca issued a statement as voting got underway Tuesday, saying that the campaign would not use traditional methods to turn out voters and adding that casting a ballot is “a personal decision and we respect whichever choice they make.”

Some Sanders allies speculate privately that the coronavirus crisis might make it more likely that Sanders stays in the race. As a longtime advocate of creating a Medicare-for-all system in which the government is the sole provider of health insurance, Sanders has said the pandemic shows precisely why universal health ­care needs to be enacted swiftly.

And he has seized on the moment to amplify his critique of the country’s stark economic divides, warning that the most vulnerable stand to suffer the harshest consequences of the pandemic and urgently need the help he has long promoted.

One Sanders campaign official, who spoke on the condition of anonymity to talk candidly, said that the changing nature of the competition — no more in-person events in the near future, and perhaps no more primaries — could be an important factor. Sanders might be freed up to advance his cause outside the traditional pressures of the horse race, should he opt for staying in, the official said.

Yet obvious opportunities for Sanders to turn the tide against Biden have all but run out. Inside the Sanders orbit, there is private concern that Sunday’s debate did not do enough to cause a major shift in the race, as some had hoped. Still, the campaign tried to project positivity, sending talking points to supporters claiming Sanders had shown he was “the best candidate to take on Donald Trump in November.”

Sanders himself has admitted in recent days that he has failed to persuade Democrats he is more electable than Biden, in a year when Democrats place enormous emphasis on finding the candidate most likely to defeat Trump. The silver lining, Sanders has argued, is that he has prevailed in the battle of ideas and has won the allegiance of younger voters.

“It really does stun me to what degree the Democratic establishment continues to ignore the needs and the ideas of younger people,” Sanders said during a “digital rally” Monday night, one of several creative events his campaign has staged to reach supporters remotely.

As he spoke Tuesday night, Sanders was still in campaign mode, pitching his ideas much as he has over the past year at rallies and town halls. “We’ve covered a lot of territory tonight,” he said.

But he appeared determined not to draw attention to the day’s nominating contests. The only visible references to the primaries were social media hashtags that flashed in the upper right-hand corner on the streaming video, such as #BernieForAZ.