“There will be an insurgency; I just don’t know who’s leading it,” said Representative Emanuel Cleaver II of Missouri. “But I can assure you that I am as certain of that as I am that today is Wednesday.”

The question of who would lead an insurgency offered Ms. Pelosi some reassurance, but it also raised the threat of the unknown. For over a year, she has known that Mr. Crowley or Representative Steny H. Hoyer of Maryland, her 79-year-old second in command and longtime rival, would be her most obvious challengers. Both are white men with roots in the more centrist wing of the party.

Now, though, she could face a race from a colleague who is neither white nor male nor particularly moderate, and that could make it easier for her diversity-minded colleagues to latch on.

House Democrats suggested a host of challengers, including one veteran lawmaker who commands deep respect in the caucus: Representative Elijah E. Cummings of Maryland.

Mr. Cummings said in an interview that he would not challenge Ms. Pelosi, but, notably, he did not bat down the possibility that he would put himself forward should she fail to secure the votes to become speaker or leader.