WASHINGTON — When Representative Jerrold Nadler campaigned two years ago to be the top Democrat on the House Judiciary Committee, he billed himself as the “strongest member to lead a potential impeachment.”
Mr. Nadler got the job, and last December, he led the Judiciary Committee as it drafted and approved two articles of impeachment against President Trump.
Now, it appears his work is only halfway done. Speaker Nancy Pelosi chose Mr. Nadler on Wednesday to serve on the team of lawmakers who will prosecute the case against Mr. Trump in the Senate. He will work alongside Representative Adam B. Schiff of California, the chairman of the Intelligence Committee, who oversaw the House’s Ukraine investigation, and five other managers.
If Mr. Schiff’s fact-finding formed the basis for Mr. Trump’s impeachment — he uncovered a campaign by the president to pressure Ukraine to investigate his political rivals — Mr. Nadler’s work provided the legal and constitutional case that Mr. Trump’s misconduct rose to the level of high crimes and misdemeanors.
He is likely to play a similar role in the Senate’s proceeding, laying out for lawmakers why the president should be removed.
Mr. Nadler, 72, is the son of a chicken farmer. He has represented the West Side of Manhattan since the 1990s and built a reputation as a loquacious defender of civil liberties. That position, and Mr. Nadler’s fierce opposition to a proposed Trump Organization redevelopment project, earned the Democratic congressman the early ire of Mr. Trump, then merely a tabloid-famous New York real estate developer.
But as chairman of the Judiciary Committee, Mr. Nadler has arguably been a bigger thorn in the president’s side. The famously partisan panel has aggressively pursued investigations of Mr. Trump’s immigration policies and of possible abuses by Mr. Trump around the special counsel’s Russia investigation.
Before the Ukraine matter emerged this fall, Mr. Nadler spent months trying to build an impeachment case based on the findings of Robert S. Mueller III’s report on Russian election interference and possible obstruction of justice by Mr. Trump. The push won him acclaim from liberals but chafed Ms. Pelosi, who conspicuously second-guessed some of his decisions to colleagues.
As a manager, Mr. Nadler brings with him a team of lawyers who were integral to the House’s impeachment proceedings, including Barry Berke, a veteran white-collar defense lawyer, and Norman L. Eisen, a former White House ethics czar and well-known liberal watchdog.
This fall, Republicans delighted in throwing Mr. Nadler’s dire warnings about a partisan impeachment back in his face as the chairman marched ahead to press charges against Mr. Trump.
“The American people are watching, and they won’t forget,” he said 21 years ago. “You may have the votes, you may have the muscle, but you lack the legitimacy of a national consensus and the Constitution. This partisan coup d’état will go down in the history of this nation in infamy.”