Joseph R. Biden Jr. usually rises before 8 a.m. at his home in Wilmington, Del., and starts his day with a workout in an upstairs gym that contains a Peloton bike, weights and a treadmill. He often enjoys a protein shake for breakfast and puts on a suit or blazer much of the time. In the evenings, he and his wife, Jill, sit down together for dinner, a ritual that was absent for much of the last frenzied year on the campaign trail.

In the intervening hours, Mr. Biden attempts to win the presidency without leaving his house.

With the coronavirus outbreak freezing the country’s public life, Mr. Biden has been forced to adapt to a cloistered mode of campaigning never before seen in modern American politics. He was unable to embark on a victory tour after the Democratic primaries or hold unity rallies with onetime rivals like Senators Bernie Sanders of Vermont and Elizabeth Warren of Massachusetts. Instead, the former vice president is in a distinctive kind of lockdown, walled off from voters, separated from his top strategists and yet leading in the polls.

For a famous backslapper like Mr. Biden, this open-ended period of captivity has tested both his patience and his political imagination. He has lamented being deprived of human contact, and he has expressed exasperation with media coverage critiquing his limited visibility compared with President Trump’s daily performances in the White House briefing room. He does not make a habit of watching the president’s briefings in full; he is said to be fixated mainly on the eventual challenge — if he wins — of governing amid a pandemic.

Interviews with dozens of people in touch with the presumptive Democratic nominee and his advisers revealed a newly detailed picture of Mr. Biden’s life in seclusion, one spent in long-distance consultation with a wide array of coalition leaders helping him map out the fall campaign and a potential administration.

Mr. Biden has revived many of the rituals of the vice presidency, including similarly formatted briefing memos and tour d’horizon-style updates from aides on the virus and the economy — all aimed at giving him the information he would need to make the weighty decisions at hand if he were in charge, except that he is not.

Fran Person, who served for years as a Biden aide and speaks with him regularly, said the detached lifestyle was unnatural for Mr. Biden, an extrovert who spent virtually his entire adult life in government.

“I can imagine, for him, you’re watching this play out, you know what needs to get done,” Mr. Person said. “You want to be right in the middle of it.”

As the temperature of the campaign rises in public, increasingly featuring caustic attacks on Mr. Biden from Mr. Trump and his allies and blunt rebuttals from Mr. Biden’s aides, the former vice president has not attempted to match Mr. Trump blow for blow on television.

For the most part, Mr. Biden is seeking to run a campaign based on something like digital-age fireside chats, offering himself as a calmly authoritative figure rather than a brawler like his opponent. In private, he voices a combination of optimism about American resilience and recognition that the country is likely to be in a bleak state on Inauguration Day.

It remains to be seen whether that approach will come to be viewed as appropriately sober or perilously passive against a tenacious and unpredictable opponent. Many Democrats remain anxious about the limitations of Mr. Biden’s position, even though Mr. Trump has slipped markedly in the polls and faces growing disapproval of his response to the pandemic.

Only a few people have seen Mr. Biden, 77, in the flesh in recent weeks. He is guarded by the Secret Service, and a pair of trusted staffers assist with his daily activities. The rare outside visitors don masks and gloves as a safety measure.

Like many professionals these days, the former vice president fills his time with conference calls. There are at least four standing calls on his daily schedule, including one with Jennifer O’Malley Dillon, his new campaign manager. There are daily briefings on the economy, public health and electoral strategy, and a less frequent session on national security.

Mr. Biden has used a television-quality video uplink from his refurbished rec room for interviews and online campaign events. But for private conversations, he prefers conferring by telephone, usually on speakerphone in his study. At times, callers deduce from rowdy background noise that Mr. Biden is working beside his German shepherds, Major and Champ.

The former vice president also places calls to mayors and governors; congressional leaders like Representative James E. Clyburn of South Carolina; elder statesmen like Al Gore; potential running mates; donors; and former rivals like Mr. Sanders and Ms. Warren. A few governors have become favorite points of contact, including Andrew M. Cuomo of New York, Jay Inslee of Washington and Gretchen Whitmer of Michigan.

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.

“It’s going to be this way,” he said, “for a little while.”

An Extrovert in Lockdown

The estate on which Mr. Biden is functionally trapped has long been a personal refuge. Nestled along a lake and recessed from the road by a long private drive, the 6,800-square-foot home took more than two years to build and Mr. Biden has said he designed it himself.

It is a home the Bidens had talked about bequeathing to his son, Beau, and that Mr. Biden later considered mortgaging or selling to help support Beau’s family as he suffered from cancer. It was at this home where Mr. Biden worked to refine the 2016 presidential announcement speech he never delivered.

Today, the house has become an almost sealed containment zone. Two political aides regularly enter and leave the house, according to people briefed on the safety restrictions put in place: Annie Tomasini, Mr. Biden’s traveling chief of staff, and Anthony Bernal, Jill Biden’s chief of staff, both of whom have worked for the Bidens on and off for more than a decade.

But several people familiar with their roles said they are not staffing the Bidens around the clock and it is not clear whether any other aides assist the candidate at home. Much of the time Mr. Biden answers his own telephone, and he frequently falls behind his limited public schedule.

The campaign has consulted physicians and health experts about safeguarding Mr. Biden, who at 77 falls squarely into a high-risk group for the coronavirus. Irwin Redlener, a clinical professor at Columbia University’s Mailman School of Public Health, said he had spoken with the campaign about health precautions, including how to handle the possibility that members of Mr. Biden’s traveling staff had been exposed.

“In terms of the safety of the staff, the candidate, what did they need to know?” said Dr. Redlener, who previously served on Mr. Biden’s public health advisory committee.

Mr. Biden has embraced the safety guidelines: He has described in interviews a careful protocol that allows him to interact with some of his grandchildren, who live nearby. They come over to play on his lawn, allowing Mr. Biden and Jill Biden to talk to them and sometimes throw them candy or ice cream from a short distance.

To interact with voters, his campaign has experimented with virtual town halls and round tables, but Democrats in the states are anxious to see more of the candidate.

Milwaukee Mayor Tom Barrett, who recently endorsed Mr. Biden, said he had prodded the campaign to do more to put him directly in front of Wisconsin voters.

“It is so critically important for him to have a presence here,” Mr. Barrett said. “I think, in some ways, Zoom and FaceTime — they’re the 2020 counterpart to what President Trump used effectively for his base, which is Twitter.”

Mr. Biden is working to adapt to those platforms; this past week he spent half an hour on a Zoom call with a nurse in Wisconsin and then contacted other members of her family by phone. But targeted video-chatting offers Mr. Biden only so many opportunities to hear from voters directly about their struggles and needs.

Ashley Ruiz, a voter in Fort Lauderdale, Fla., who recently participated in a “virtual rope line” with Mr. Biden, said she had found him eager to share his ideas about education and child care. But Mr. Biden grew most animated when he detected the presence of her two sons — ages 10 and 7 — along with her red-nose pit bull, Kacie.

Mr. Biden, she said, was determined to communicate with her 7-year-old son, who has autism and, like Mr. Biden, a stutter. “He said to my son, ‘I want you to know you can do anything,’” Ms. Ruiz said, recalling that Mr. Biden had told her, “When I’m president, I will care for your family like they’re my family.”

Defining the substance behind that promise is what mainly occupies Mr. Biden’s time.

Seeking Bigger Ideas

Even before Mr. Biden entered his state of near-quarantine, he was telling associates that he feared the onset of a national catastrophe. In mid-March, Mr. Biden told one confidant that he was concerned that the country could face another Great Depression, sharing that he had discussed the possibility with Lawrence H. Summers, the former treasury secretary.

That dark contingency now looks more plausible than ever. In the daily briefings he receives about public health and the economy, Mr. Biden seeks the kind of minute information he would need to make important policy decisions — if only he were in a position to do so.

Several participants in the briefings said Mr. Biden probes extensively about the mechanics of how money and medical resources are being distributed around the country. Spurred by beleaguered governors, he regularly presses his team about the steps Washington might take to shore up shattered state budgets.

“There is that sort of suspended quality to things in that you’re not making a decision that’s urgent and that people have to carry out today,” said Senator Chris Coons of Delaware, a close Biden ally. Still, he described “a real sense of imminence” because the aides briefing Mr. Biden in lockdown today could well be managing the government response in 10 months.

“It’s like the relief pitcher warming up in the bullpen, knowing you only get a couple more pitches and then you’re going out on the mound,” Mr. Coons said.

One of those advisers, Vivek Murthy, the former surgeon general, said Mr. Biden wanted to stay on top of both the large-scale policies aimed at containing the virus and on the precise efforts of local governments and medical facilities. Though most people on the calls are former government officials, a view from the front lines of medicine comes from a member of the Biden family: Howard Krein, the former vice president’s son-in-law, who is a doctor in Philadelphia.

In one briefing, Dr. Murthy said it hit Mr. Biden hard to learn that hospitals were barring people from visiting dying family members. “He knows what it’s like to lose people and to have your life turned upside down,” Dr. Murthy said.

A daily call on the economy and a somewhat less frequent briefing on national security are stocked with veterans of the Obama administration, including Ben Harris and Jared Bernstein, who served as economic advisers to Mr. Biden in the vice presidency, and Antony J. Blinken and Jake Sullivan, his former national security advisers. Murmurs about Mr. Summers’s quiet role advising Mr. Biden have alarmed some progressives, who saw the former Harvard president as closely aligned with Wall Street during the last recession.

It is not clear, however, that any ideological camp has a full claim on Mr. Biden’s ear right now: On the economic calls, Mr. Biden regularly seeks insight into the thinking of his party’s populist wing, inquiring by name about Ms. Warren, Mr. Sanders and a third liberal, Senator Sherrod Brown of Ohio.

So far, Mr. Biden’s policy huddles have yielded proposals to contain the immediate damage of the pandemic. But his allies expect he will soon go substantially further with a national-emergency agenda, likely to include huge new promises on economic stimulus, infrastructure, climate change and student debt.

The test ahead for him, however, is not just defining a bold agenda, but also communicating it from a desk in his house as Mr. Trump makes ruthless use of his bully pulpit.

Mr. Inslee, who endorsed Mr. Biden on Wednesday after conferring with him privately about broadening his climate agenda, said he urged Mr. Biden to put safety first. Democrats, he said, “understand that we’re not going to hear from our candidate as much as we would if we didn’t have a pandemic.”

“It’s really important that he take care of his health right now,” Mr. Inslee said. “It’s important for all of us.”