Mr. Sanders has appeared eager to put himself front and center for his supporters, holding live stream events on the virus nearly every night and pushing out a long list of policy proposals to handle the outbreak that included providing every American with a check for $2,000 a month.

In a sign of his political influence, he threatened on Wednesday afternoon to hold up the economic stimulus bill if Republicans continued to fight unemployment benefits that they feared would be larger than some people’s wages — the reason for his sarcastic denunciations in the Senate chamber.

“While we do our best to address these crises, it is extremely important that we try to understand how we got to where we are today, and the need to bring about fundamental reform of American society,” Mr. Sanders said during a live stream event on Wednesday night, after running viewers through major elements of the stimulus bill.

Many of his supporters are still holding out faint hope that he can win the nomination, arguing that the coronavirus outbreak has made even unlikely scenarios possible. Already, many states have pushed their primaries back to June 2, making it impossible for Mr. Biden to clinch the nomination before then. There are murmurs among some allies that Mr. Sanders intends to stay in at least until the primary in New York, which is scheduled for April 28 but could be pushed back to June 23.

Some want him to stay in the race indefinitely because his candidacy provides him the megaphone to shape the narrative of the progressive agenda, and will give him leverage as he seeks policy concessions from Mr. Biden and influence over the party’s platform.

Some close to him suggested that his coronavirus outreach was a way to keep his supporters motivated and engaged during this strange time of suspended animation, so that the campaign can jump-start them into action if he decides to rev his candidacy back up.

His detractors, however, point out that he has chosen to hold his own events and speak to his own supporters but until Wednesday had largely left the congressional proceedings to others — including his former rival Senator Elizabeth Warren, who was active in helping to shape the rescue bill. On Sunday, when fellow Senate Democrats blocked an action on the bill that delayed progress, he skipped the vote, instead remaining in Burlington to air a live stream with Representatives Alexandria Ocasio-Cortez, Ilhan Omar and Rashida Tlaib.