A Top Biden Aide Is Taking the Reins of His Re-election Campaign

President Biden has approved a shake-up of the leadership of his campaign, and will dispatch a top White House aide to take over functional control of his re-election effort just as former President Donald J. Trump appears to be seizing control of the Republican primary contest to oppose him.

The aide, Jennifer O’Malley Dillon, who was the campaign manager for Mr. Biden’s 2020 campaign and has served as a deputy chief of staff in the White House since he became president, will move to the Biden 2024 headquarters in Wilmington, Del., and direct the campaign’s efforts, according to five people familiar with the discussions.

It is unclear precisely what title Ms. O’Malley Dillon will take at the campaign or when the announcement will be made, though it could come later this week. Julie Chávez Rodríguez, the campaign’s manager since shortly after it began in April, is expected to retain that title.

“Our campaign manager is and will continue to oversee the president’s re-election efforts, and this campaign will remain laser-focused on defeating Donald Trump and MAGA extremism at the ballot box this November,” said Michael Tyler, the campaign’s communications director.

The move formalizes a setup in which Ms. O’Malley Dillon has for months overseen the campaign’s direction from Washington.

When the Biden campaign held a December retreat for staff members at its headquarters, it was Ms. O’Malley Dillon who led the proceedings — not Ms. Chávez Rodríguez, according to two people who attended the session but were not authorized to speak publicly about it.

Donors, operatives, elected officials and other Democrats supportive of Mr. Biden have been increasingly worried about a campaign structure that had major and even minor decisions