At his request, Mr. Biden talks at least once daily to a voter or campaign volunteer — the kind of people he would meet constantly on the trail. And he regularly phones allies to express sympathy or support, including a call to Ms. Warren when he learned that one of her brothers had died of the coronavirus.

Ms. Whitmer, a potential running mate for Mr. Biden, said the former vice president had been deeply engaged with the details of the outbreak in her state. He had offered advice and commiserated over the isolation brought on by the virus, and how it had barred them from performing consoling tasks like visiting mourners and medical workers.

“I think that’s why he’s calling and reaching out and trying to keep a pulse on what’s happening,” Ms. Whitmer said. “It’s not a great substitute for personal interaction, but it’s a way to stay connected.”

The Biden campaign declined to make him available for an interview. But the former vice president has at times spoken publicly about his isolation. “I’m chomping at the bit,” Mr. Biden told reporters a month ago. “I wish I were still in the Senate, you know, being able to impact on some of these things. But I am where I am.’’

For a team that employed a relatively skeletal digital operation throughout the primaries, the sudden shift toward online campaigning has been abrupt. At times, Mr. Biden has appeared out of his comfort zone and he continues to express a kind of chuckling disbelief that his basement has become a makeshift studio. Advisers acknowledge that they have considerable catching up to do on sites like Facebook and YouTube.

Mr. Biden is also facing pressure from donors to ramp up his at-home fund-raising activities, and from leaders in the states who want to see him beaming more often into key battlegrounds. To that end, he has recently conducted a series of interviews with local television stations in markets like Detroit and Pittsburgh, with more planned.

But Mr. Biden is burrowing in for the long haul, telling donors this month he did not anticipate holding traditional public events anytime soon.