A day after winning another string of dominant victories that moved him closer to the Democratic presidential nomination, Joe Biden’s campaign was working to reboot amid broad concerns within the party that his current operation is ill-equipped to match President Donald Trump’s behemoth reelection effort.

Biden pulled off the most stunningly swift turnaround in modern political history with a relatively small staff, underwhelming fundraising and a campaign occasionally marked by dysfunction and turmoil.

After finishing fifth just four weeks ago in New Hampshire, there were questions over how his campaign could gracefully end. But Biden now has won at least 15 of the last 21 voting states, making him the candidate likeliest to face Trump in a highly polarized, extremely expensive general election.

Biden’s advisers are taking steps to expand virtually all parts of his shoestring campaign operation, from finance, field and communications departments to the senior leadership team, answering the concerns of senior Democrats who are bracing for a new wave of assaults from Trump.

That effort will occur even as Biden continues to battle for delegates with Sen. Bernie Sanders, I-Vt., who announced Wednesday that he would stay in the race as he issued policy demands to Biden on issues like health care.

“We will be building out every team here,” Biden senior adviser Anita Dunn said Wednesday, after making clear that the primary mission of the campaign remains acquiring enough delegates to win the nomination. She suggested that would be done at least in part by embracing aides to former candidates, many of whom have endorsed Biden in recent days.

“We are seeing an enormous amount of talent from people on other campaigns. We would hope that we would be able to have some of those people joining this campaign.”

Dunn took on new management and strategic responsibilities shortly before the New Hampshire primary. She is likely to shift out of some of that responsibility in the coming months, leaving open the possibility of shifts at the top of the operation, according to a person familiar with the campaign’s discussions who was not authorized speak publicly.

In recent weeks, the campaign has relied on Jen O’Malley Dillon, the campaign manager for former congressman Beto O’Rourke, D-Texas, who helped the Biden campaign retool ahead of the Nevada caucuses and has offered strategic advice on a volunteer basis. No announcement has been made about her taking on a more formal role.

At the same time as he tries to finish off Sanders and bulk up his campaign, Biden also is planning for a vice presidential selection process later this spring, following the recommendation of the Bipartisan Policy Center that any vetting begin at least two months before a nominating convention.

Throughout the primaries, even some of Biden’s top allies have be confounded by the struggles of his campaign operation and worried about this period, when the nomination is not yet secured but the incumbent president can aim his firepower at the leading opposing candidate.

Several Democrats involved in the campaign had front-row seats in 2012 when President Barack Obama used a massive spring and summer advertising offensive to define his Republican challenger, Mitt Romney, in swing states as a predatory businessman who was not in touch with the concerns of regular Americans.

Unlike Romney, Biden will be assisted by a constellation of outside Democratic groups, including Priorities USA and American Bridge, which announced this week a strategic decision to defend Biden this spring in key swing states, even though he has not yet locked up the nomination.

As it stands now, the campaign’s senior leadership remains a kitchen cabinet of new and old advisers, a setup Biden has used throughout a political career that spans more than four decades. His former chief of staff, Steve Ricchetti, functions as campaign chairman; his longtime adviser Tom Donilon is the strategist; the candidate’s sister Valerie Biden Owens is a close adviser, and the campaign apparatus is overseen by Dunn, a veteran of the Obama campaigns, and Greg Schultz, the campaign manager.

“He has a very loyal group around him, and that group gives him comfort, and that group is still going to be there,” said David Axelrod, a former strategist for Obama who has worked closely with Dunn. “But there has to be room for a more formal and developed campaign structure that does all the very complex blocking and tackling.”

The new planning has been enabled by a windfall in campaign contributions and endorsements that has effectively put the bulk of the party apparatus at his disposal. The organizers for Unite the Country, the super PAC backing Biden, said they raised $10 million over the past 10 days and have $30 million in additional commitments.

“The good news is the entirety of the Democratic Party and the Democratic Party establishment is available to them and willing to help them,” said one senior adviser to a onetime rival, who like others spoke on the condition of anonymity to discuss private conversations. “The question is can they retool and bring in a second wave of talent and leadership?”

But the campaign’s abilities continue to face criticism. Even as Biden won every county in Michigan this week, local Democrats voiced concern that his light footprint in the state foretold a fall repeat of 2016’s disaster for Democrats, when Hillary Clinton counted Michigan as a safe bet for her campaign until it was too late. Biden also has only a scattered presence in three states that will vote next week and that his campaign believes will play roles in the general election – Florida, Arizona and Ohio.

Donors who had been sitting on the sidelines or supporting other candidates have complained in recent weeks that they are unable to connect directly with Biden or top campaign officials, saying there are not enough finance directors to field the incoming requests.

Millions of dollars in donor commitments have flowed to the campaign since Super Tuesday. Endorsements are coming so quickly that campaign officials are learning about some of them on Twitter.

“This was a campaign that was running in a very lean fashion. It’s great, because it saved the money they needed. But now it’s created kind of a logjam for people like me,” said Alan Kessler, a longtime Biden donor and Democratic fundraiser. ” . . . I’m not the only one getting these emails and calls. People are a little anxious.”

Just this week, Rufus Gifford, who ran President Obama’s 2012 reelection finance operation, emailed hundreds of donors and fundraisers in his network to help the campaign counter Trump’s fundraising machine, and to help direct donations to the national and state Democratic parties.

“Now it’s about building a long-term infrastructure, making sure the money continues to flow,” Gifford said Wednesday. “You have the recipe for a real success and a real coalition to pull the voters across the finish line. The campaign has got to scale [up]. You can’t do this on a shoestring.”

As part of his march toward the nomination, Biden also is planning to offer Americans a fuller picture of how he might govern, part of his effort to draw a sharp contrast between his hypothetical tenure and Trump’s polarizing and unorthodox politics. The aim is to convey the potential for renewed stability, an emphasis on competent governance and a restoration of American leadership around the globe.

“At this moment, there’s so much fear in the country,” he said in remarks Tuesday night that served as a template for his future pitch. “There’s so much fear across the world. We need presidential leadership that’s honest, trustworthy, truthful and steady.”

On Thursday, during an address from his hometown in Wilmington, Delaware, Biden is planning to address the coronavirus pandemic in an attempt to counter a response from the White House that has downplayed the severity of the global crisis.

Campaign leaders say they are not yet focused on planning for the early days of the administration, should Biden win the White House. But among a broader group of outside allies, conversations that were previously unthinkable have started quietly taking place, including when Biden may form a transition team and how he would craft an agenda to implement in the first 100 days of a presidency.

Biden himself has from time to time begun openly ruminating about a potential cabinet – last week telling O’Rourke, seemingly off-the-cuff, that he could lead the effort on gun-control policy – and about finding a vice president who could be to him what he was to Obama.

“For me, I think the most important thing in choosing a vice president is whether or not the person is simpatico with me,” he told MSNBC on Monday. He stopped himself, to say it was presumptuous to talk about it. And then he continued to talk about it.

“We can disagree on tactic, but not on strategy,” he said of a potential partnership. “That’s the first test – and there are a number of women, and African-Americans as well, who meet that criteria for me.”

He is almost certain to pick a woman to be his vice presidential running mate, according to allies in close contact with the campaign. During the MSNBC interview on Monday, Biden also said that it was “very important” that his pick will have been tested on the presidential campaign stage, which could narrow his options.

Those close to several of his former rivals – including Sens. Elizabeth Warren, D-Mass., Amy Klobuchar, D-Minn., and Kamala Harris, D-Calif. – said that no conversations have taken place.

“It wouldn’t shock me at all if he welcomes former rivals,” said former senator Chris Dodd, who remains in close contact with Biden. “He doesn’t hold grudges. Biden’s been around too long to understand that doesn’t get you too far. His instincts would be to be inclusive.”

The overriding goal for now, however – one that has taken on new urgency amid the coronavirus scare and a tumbling stock market – is casting Biden as a president who could allow the country to exhale and worry less about what the government was doing.

“He’s emerging as that stable figure that the country needs,” said Rep. Tim Ryan, D-Ohio, a former presidential candidate who has backed Biden. “It’s not going to be the circuslike atmosphere that is happening right now.”

– – –

The Washington Post’s Holly Bailey in Detroit and Michelle Ye Hee Lee contributed to this report.