And on Wednesday, it fell to Mr. Nadler, who earned his law degree by attending evening courses while serving in the New York State Assembly, to oversee Wednesday’s debate on the resolution that formally approved the impeachment managers, allowing the articles of impeachment to be sent to the Senate. Behind him sat Ms. Pelosi, Mr. Schiff and the other managers: Mr. Jeffries, Representatives Val B. Demings of Florida, Jason Crow of Colorado, Zoe Lofgren of California and Sylvia R. Garcia of Texas.

Ms. Lofgren is the sole House Democrat to have participated in the past three presidential impeachment processes, having worked as a committee aide during the proceedings against Richard M. Nixon and served on the Judiciary Committee during the impeachment of Bill Clinton. And while Ms. Demings does not have a formal background as a lawyer, she was the first woman to be police chief of Orlando, Fla., and sits on both the Intelligence and Judiciary Committees, giving her a prominent perch to participate in the impeachment inquiry.

The two freshmen lawmakers named to the group, Ms. Garcia and Mr. Crow, both bring critical perspectives for the arguments to remove Mr. Trump. Ms. Garcia, one of the first two Latina women to represent Texas in Congress, was a former judge, while Mr. Crow, a former Army ranger and litigator, is considered an authority on national security matters, which are at the heart of the Democratic argument for Mr. Trump’s removal.

And Mr. Schiff, a former federal prosecutor in Los Angeles who secured the conviction against the F.B.I. agent, won his seat by defeating James E. Rogan, a Republican who had served as an impeachment manager in the 1999 Clinton trial. In a quirk of history, Mr. Rogan’s predecessor had also worked on an impeachment inquiry, into the Watergate break-in that led to Nixon’s resignation.

Ms. Pelosi began conducting individual meetings with lawmakers this month to gauge their interest in the role of manager, according to a person familiar with the meetings but not authorized to discuss them publicly. She called most of the group on Tuesday to inform them of their selection, and then met with the full group privately Wednesday morning.

“This is all about protecting the Constitution,” Ms. Demings told reporters as she left the news conference. “I’ve taken four oaths in my lifetime — two as a law enforcement officer and two here — and I take them very, very seriously.”