WASHINGTON — Since its creation in 1813, the House Judiciary Committee has served as the backdrop to debates over the most contentious issues in American history, including a woman’s right to vote, immigration and civil rights. It has either held or recommended impeachment proceedings against three presidents: Andrew Johnson, Richard M. Nixon and Bill Clinton.

Now President Trump is on that list.

On Wednesday, the judiciary panel — 24 Democrats and 17 Republicans — is to open the second phase of Congress’s inquiry into Mr. Trump’s effort to enlist Ukraine to dig up damaging information on his political rivals. Four constitutional scholars will testify on what constitutes an impeachable offense, a prelude to the panel’s consideration of articles of impeachment.

Here are some key committee members to watch:

Jerrold Nadler, Democrat of New York and chairman of the committee

The son of a Jewish chicken farmer, Mr. Nadler has a long and not happy history with the president. The two fought bitterly in the 1980s over a real estate development Mr. Trump sought to build on the Upper West Side of Manhattan. Meticulous and thorough — he is never seen without a stack of briefing papers — Mr. Nadler, 72, faded from view when Representative Adam B. Schiff, the chairman of the House Intelligence Committee, took the reins over the Democrats’ impeachment inquiry. Now it’s Mr. Nadler’s turn.

Doug Collins, Republican of Georgia, the ranking member

Fast-talking, ambitious and a fierce defender of the president in the Capitol and on Fox News, Mr. Collins, 53, has lately been in the news over a dispute between Mr. Trump and Gov. Brian Kemp of Georgia over who should fill the Senate seat being vacated by Senator Johnny Isakson, who is retiring early. Mr. Trump wanted Mr. Kemp to appoint Mr. Collins, figuring Mr. Collins would be an attack dog during a Senate impeachment trial. Mr. Kemp appointed someone else, but Mr. Collins may seek the seat anyway.