Former vice president Joe Biden named Jen O'Malley Dillon as his new campaign manager Thursday, a major shake-up that comes as the party's leading candidate plans an organizational expansion to prepare for the general election.

The move is intended to quell concerns raised in recent weeks by senior Democratic strategists about the leadership structure of the Biden campaign, which has been beset by underwhelming fundraising, scant staffing resources and organizational miscues during the early nominating contests.

"She will be a tremendous asset to a campaign that is only growing and getting stronger as we prepare to take the fight to Donald Trump this fall," Biden said in a statement accompanying the announcement.

The campaign shuffle is an acknowledgment that while Biden has had a remarkable recent run of victories - at least 15 of the past 21 contests - his operation was not up to the challenge posed by President Donald Trump if Biden wins the nomination.

After Biden performed well below expectations in the Iowa caucuses, Anita Dunn, a senior adviser who previously worked for President Barack Obama, took operational control of the campaign, sharing responsibilities with Biden's original campaign manager, Greg Schultz.

Dunn, who helped Biden prepare for a possible 2016 run for president, will also continue with the campaign, returning to her role as a senior adviser to Biden. Schultz, who prepared and built the Biden campaign and oversaw initial hiring and delegate strategy, will stay on in a new role. "I will value his continued input on this campaign," Biden said in the announcement.

"I look forward to building out the Biden coalition and doing the necessary preparations for a possible general election and making sure we coordinate with the local, state, and national Democratic infrastructure," Schultz said in a statement to The Washington Post.

In the wake of multiple victories in Tuesday's presidential primary contests, Biden's advisers acknowledged 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.

"Jen is in a league of her own," said Guy Cecil, the chairman of Priorities USA, a super PAC that has committed to helping Biden. "She is smart, strategic and a terrific team builder. I can't imagine a better person to lead us into November."

Robby Mook, who managed Hillary Clinton's 2016 campaign, also praised the new leadership structure.

"She comes to this with all the different pieces of the tool kit," Mook said of O'Malley Dillon. "The best campaign managers are talented and prepared, and she is coming with both."

He also favored Schultz's new role as one of the point people for coordinating with the Democratic National Committee.

"You want someone heading up that operation who has the deep trust of the candidate and of the inner circle," Mook said. "And you want someone with deep experience running the state operations, and Greg has both of those things."

Biden's new campaign manager also has deep ties across the party. O'Malley Dillon, 43, served as battleground states director for Obama's 2008 campaign and deputy campaign manager for his 2012 reelection effort. She was also executive director for the Democratic National Committee during his first term, putting her in the inner circle of Obama's political advisers.

More recently, she helped to lead an early 2019 Democratic effort to create a new for-profit data exchange to allow for greater information sharing between Democratic campaigns and affiliated groups, an effort party leaders see a crucial for catching up with the Republican data program.

O'Malley Dillon later served as the presidential campaign manager for former congressman Beto O'Rourke, D-Texas, relocating to El Paso. After O'Rourke's campaign ended, she volunteered as a campaign adviser for Biden before the Nevada caucuses, and then continued on as an informal adviser to senior Biden campaign officials in recent weeks.

O'Malley Dillon will work out of the campaign's Philadelphia headquarters.

"Vice President Biden is turning out voters at record levels and building the broad coalition we need to ensure Donald Trump doesn't get a second term," O'Malley Dillon said in a statement. "It's an honor to help make him the 46th President and I'm ready to get to work."