After four years in the minority, Republicans will be reclaiming the gavels of all 21 House committees when the 118th Congress convenes in January. Control of these committees gives Republicans not only legislative muscle, but investigatory and oversight powers as well.

Committee composition will disclose a great deal about the congressional leadership’s priorities — who their friends are, and with whom they must curry favor. Leader Kevin McCarthy, who is fighting to get the speaker’s gavel, needs to do just that with far-right members of his caucus. 

For Republicans, committee chairs are nominated by the steering committee — a 30-member body made up of the top GOP House leaders and regional representatives — and are later ratified by the GOP caucus. Democratic chairs are chosen by seniority. The House GOP has adopted the practice of allowing its members to serve as top Republican on a committee for three terms, or six years. Democrats have no such rule. 

If elected speaker, Mr. McCarthy will be the third Republican to hold the post in the last 10 years. The other two, Speakers Boehner and Ryan, both had fraught relationships with the far-right members of their caucus, ultimately leading to Mr. Boehner’s resignation and Mr. Ryan’s retirement. Mr. McCarthy has learned from their mistakes, and has promised key committee posts to the same members who brought down his old bosses. 

Seats on committees are generally awarded based on fundraising prowess, loyalty to leadership, and ability to advance the party’s agenda. In 2016, Congressman Thomas Massie said that committees are based on “dues” paid.

“They told us right off the bat as soon as we got here, ‘These committees all have prices, and don’t pick an expensive one if you can’t make the payments,’” the Kentucky native said. Promises of plum committee assignments allow congressional leaders to curry favor with the rank-and-file, a process now playing out. 

Nothing is more indicative of Mr. McCarthy’s embrace of his right flank than his relationship with Congressman Jim Jordan of Ohio. Mr. Jordan, a founder of the far-right House Freedom Caucus, was one of the central players in bringing down Mr. Boehner and subsequently ending Mr. McCarthy’s first bid for speaker in 2015. Now, Mr. Jordan is one of Mr. McCarthy’s four transition team members, and is likely to be chairman of the Judiciary Committee in the next Congress. 

The Oversight and Reform Committee is Congress’s main investigatory standing committee, charged with overseeing all aspects of government affairs. The chairman will be Congressman James Comer, a four-term representative of Kentucky who has been the lead Republican on the committee since 2020. Mr. Comer told NBC News’s Chuck Todd that he has dozens of investigations planned for the coming session. “These are things that are going to be priorities for us as a committee: waste, fraud, abuse, and mismanagement,” he said. 

Beyond the standing committees that exist regardless of congressional control, Republicans could set up their own select committees, as Speaker Pelosi did with the January 6 committee and Speaker Boehner did with the Benghazi committee.

Mr. McCarthy has already said he plans to establish a select committee on China, investigating threats from Beijing and the Biden administration’s response. Other select committee topics could include the president’s son, Hunter Biden, the southern border, and the withdrawal from Afghanistan. 

Facing challenges from conservative members in his quest for the speakership, Mr. McCarthy also has made an alliance with one of the most far-right members of the House — Congresswoman Marjorie Taylor Greene of Georgia. 

Last year, every Democrat and 11 Republicans voted to remove Ms. Greene from her committees after a series of antisemitic social media posts were unearthed. Mr. McCarthy has promised to reinstate Ms. Greene as an active committee member, which could explain why she has offered a full-throated endorsement of a McCarthy speakership. Ms. Greene has said she would like to serve on the judiciary and oversight committees, both of which are likely to aggressively investigate the Biden administration. 

Just as Ms. Greene was banned from serving on committees, Mr. McCarthy plans to remove Democrats from their posts. Representatives Ilhan Omar, Eric Swalwell, and Adam Schiff are all likely to be removed for varying reasons. 

Mr. Schiff believes that his potential removal has nothing to do with retribution, however. He believes it is about Mr. McCarthy shoring up support from his caucus. “McCarthy’s problem is not with what I have said about Russia. McCarthy’s problem is, he can’t get to 218 without Marjorie Taylor Greene and Paul Gosar and Matt Gaetz. And so he will do whatever they ask. And, right now, they’re asking for me to be removed from our committees,” the Democrat of California told CNN. 

Who sits on which committees has real policy implications, especially in a Congress divided so closely. Last year, Congresswoman Kathleen Rice of New York defeated Congresswoman Alexandria Ocasio-Cortez for a seat on the House Energy and Commerce Committee. Months later, Ms. Rice was the deciding vote in killing drug pricing reform on the panel. Mr. McCarthy, now having the same size majority that Democrats had then, could have legislation decided by one or two members depending on who sits on which panel. 

Committee assignments are one of the few carrots that congressional leadership has in rewarding members. Now, as Mr. McCarthy fights for his potential speakership, he is using that power to appease members, advance the Republican agenda, and manage his caucus.