President-elect Joe Biden will announce three key appointments to his incoming White House staff Tuesday.

Rep. Cedric Richmond (D-La.) will leave Congress to take on a senior adviser role in the Biden administration handling public engagement, while Biden campaign manager Jen O’Malley Dillon will serve as deputy chief of staff and longtime Biden confidant Steve Ricchetti will become a counselor to the president, people familiar with the matter said ahead of Tuesday’s announcement.

Richmond — who was considered a possible contender for Biden’s chief of staff, a position that ultimately went to longtime Biden adviser Ron Klain — has a press conference scheduled for Tuesday where he is expected to announce that he will be leaving the congressional seat he has held since 2010 for a White House role.

The 47-year-old’s role will mimic that of Valerie Jarrett during the Obama administration, during which she oversaw the Offices of Public Engagement and Intergovernmental Affairs.

Richmond, a former Congressional Black Caucus chairman who served as a Biden campaign co-chair, had the strong backing of Democratic kingmaker and House Majority Whip James Clyburn (D-SC) for a top administration post.

Upon hearing reports of Richmond being given a top job, the South Carolina Democrat appeared elated, telling reporters that the news was “great” before describing Richmond as “very gifted, very energetic.”

It was Clyburn’s endorsement of Biden in the South Carolina Democratic presidential primary that revived his candidacy and catapulted him back to front-runner status following dismal showings in Iowa and New Hampshire.

Biden’s ascent to the nomination is largely credited to his dominating performance in South Carolina.

O’Malley Dillon, who managed the former vice president’s 2020 campaign and worked on both of President Barack Obama’s White House bids, had long told friends she did not want to take on a role in government, according to CNN.

The network reported Monday that despite this, she will take on Jim Messina’s role from Obama’s first term handling the operations portfolio.

The longtime Democratic political operative, 44, became the first woman to manage a successful Democratic presidential campaign when Biden was declared the winner of the 2020 race.

The only other woman to break that glass ceiling was former White House counselor Kellyanne Conway, who managed President Trump’s 2016 campaign.

Prior to joining the Biden campaign in March, O’Malley Dillon served as campaign manager for Rep. Beto O’Rourke’s presidential bid before he dropped out of the race in November 2019.

Ricchetti, a longtime lobbyist and Biden ally, previously served as Biden’s chief of staff during some of his vice presidency. It is not clear what his specific responsibilities will include in his new position as counselor to the president.

A Biden transition spokesperson did not immediately respond to The Post’s request for comment on the administration appointments.

Unlike cabinet positions, none of the three posts requires Senate confirmation. Cabinet picks are not expected from Team Biden for another few weeks.

As the Biden transition team begins to map out a possible administration, Democrats in the House of Representatives, which Richmond is leaving for the White House, are preparing for their caucus to face leadership elections.

Speaker Nancy Pelosi (D-Calif.), Majority Leader Steny Hoyer (D-Md.) and Clyburn are all expected to easily hold on to their respective seats for another term.

Once that is done, though, Pelosi will need to convince the 219 Democrats in the chamber to vote for her as House speaker during a January floor vote.

The House’s highest-ranking Democrat will need 218. She had 15 members of her party vote against her for the speakership in 2018.

Confronted with a shrunken majority, House leaders are discouraging fellow Democrats from taking jobs with the incoming Biden administration — out of concern that Republicans could nab any vacated seats, sources told The Post on Sunday.

Insiders variously accused Pelosi and Hoyer of urging Dems to stay put to preserve their fragile majority.

“Nancy is telling House members, ‘Now is not the time to leave,’” said a Democratic Party official who’s been briefed by Democratic congressional reps.

Another House insider said Hoyer told the Biden transition team not to poach its members because of the party’s slim majority following the Nov. 3 elections.

With Post wires