Outside the White House on Monday, the eve of the first hearing to investigate the Capitol riot, Representative Kevin McCarthy had an insult and a threat for the two members of his party daring to participate in the inquiry into how and why a pro-Trump mob attacked the Capitol on Jan. 6.

He derided Representatives Liz Cheney of Wyoming, a staunch conservative and member of a storied Republican family, and Adam Kinzinger of Illinois, a six-term congressman and Air Force veteran, as “Pelosi Republicans,” referring to Nancy Pelosi, the House speaker who chose them to sit on the special panel investigating the assault. As the minority leader, he suggested he might try to strip them of other committee assignments as punishment.

Around the same time, Ms. Pelosi made it clear that the pair would have prominent roles in the proceedings. Ms. Cheney would be cast in the spot traditionally played by the ranking member of a committee, afforded the chance to make an opening statement immediately after the chairman, Representative Bennie Thompson, Democrat of Mississippi.

The divergent moves reflected the unusual place in which Ms. Cheney and Mr.
Kinzinger find themselves as the investigation gets underway — ostracized by their own party and embraced by Democrats as the only Republicans willing to demand a full and bipartisan accounting for the worst attack on Congress in centuries.