Rep. Diana DeGette announced suddenly on Monday that she was abandoning her bid for the No. 3 job in the House Democratic leadership, ending the only official challenge to one of the party’s top leaders.

DeGette (D-Colo.) had challenged Rep. James E. Clyburn (D-S.C.), the highest-ranking African American in House leadership, for the majority whip post. But facing a backlash from members of the Congressional Black Caucus, DeGette dropped her bid — ensuring, for now, that Clyburn will remain in the top ranks.

Any major shake-up in the Democratic leadership now depends on whether a small group of incumbents and freshmen can muster the votes to keep top leader Nancy Pelosi (D-Calif.) from seizing the House speaker’s gavel in January. If that bid is successful, it could kick off a wholesale scramble that could also threaten Clyburn, the current assistant Democratic leader, and Steny H. Hoyer (D-Md.), who is seeking to move from whip to majority leader when Democrats take control in January.

“Since my announcement, I have been heartened by the backing I have received across the caucus,” DeGette said in a statement. “Over the last few days, however, many of my supporters have expressed concern about pressure they are receiving to return the three senior leaders to their posts without opposition.”

DeGette, who has long served as chief deputy whip, launched her campaign after the Nov. 6 election by touting her experience in rounding up support for difficult pieces of legislation — implicitly making the case that Clyburn, 78, was not up to or interested in the task.

But the challenge upset backers of Clyburn, a former Congressional Black Caucus chairman and a revered figure among the caucus’s roughly 50 African Americans — who bristled at the notion that the caucus’s top tier could be all-white.

“Out of the three of the leadership positions, he is the only one with announced opposition,” Rep. Cedric L. Richmond, the current Congressional Black Caucus chair, said last week. “I just think it is offensive and insulting.”

Meanwhile, the prospect of a specific challenger to Pelosi remained unclear. Rep. Marcia L. Fudge (D-Ohio) is mulling a run against her but said she would not make a final decision until next week at the earliest.

A letter signed by members determined to vote against Pelosi could be released as soon as Monday, though two aides familiar with it said it could have fewer than 20 names — giving the opponents a razor-thin margin as they seek to unseat the 78-year-old veteran leader.

The size of the Democratic majority remains in flux, but Democrats have already won 232 seats with five races still undecided, according to the Associated Press. All those races have Republican incumbents, but the Democratic challenger is ahead in only one of them.

If the current leads hold in those races, Democrats would have won 233 seats — a 16-seat majority. That means Pelosi could lose as many as 15 Democratic votes when she stands for election as speaker on Jan. 3.