Career Official Expected to Temporarily Lead Justice Dept.

However, Mr. Trump bypassed that system in 2018 after he ousted Mr. Sessions as attorney general, invoking the Vacancies Reform Act of 1998 to install Matthew G. Whitaker, who had been Mr. Sessions’s chief of staff, as acting attorney general instead of permitting the deputy attorney general, Rod J. Rosenstein, the next Senate-confirmed official in the order of succession, to fill that role.

The Justice Department’s Office of Legal Counsel signed off on Mr. Trump’s maneuver as lawful, establishing a precedent that gives presidents greater flexibility to decide who can temporarily serve as the nation’s top law enforcement officer during a vacancy. The Biden team appears to be relying on that same tactic for Mr. Biden’s installation of Mr. Wilkinson.

John Carlin, the former head of the National Security Division during the Obama administration, is expected to become the acting deputy attorney general once Mr. Biden is sworn in, according to people briefed on the transition decision.

Once Lisa Monaco, Mr. Biden’s choice for deputy attorney general, is confirmed, Mr. Carlin is to become her top deputy. Ms. Monaco was the head of the National Security Division before Mr. Carlin, and the two are known to be close allies.

Mr. Carlin and Mr. Demers are also longtime friends; they were classmates in law school.

Members of the Biden transition team expect that Judge Garland will face little opposition during his confirmation process, as key Republicans including Senator Lindsey Graham of South Carolina, the outgoing chairman of the Senate Judiciary Committee, have expressed support for his nomination. Other top Republicans including Senator Mitch McConnell of Kentucky, Mike Lee of Utah and Susan Collins of Maine supported Judge Garland in 2017 when Republicans floated him as a potential pick by Mr. Trump to run the F.B.I.

Once confirmed, Mr. Biden has said that Judge Garland’s his top priority will be to restore the department’s independence from the White House, a norm that was deeply eroded by Mr. Trump. Mr. Barr was broadly seen as willing to serve the president’s political agenda for the greater part of his tenure.

Complicating his job, Judge Garland will have to navigate demands from some Democrats to investigate Mr. Trump and from Republicans to provide more insight into the ongoing federal tax fraud investigation into Mr. Biden’s son, Hunter Biden.

Charlie Savage contributed reporting.