The Constitution grants the House the power to impeach executive branch officials for “treason, bribery or other high crimes and misdemeanors,” but what constitutes such crimes has traditionally been defined by the majority party of the House. A vote to impeach takes a simple majority in the House, but a two-thirds vote is needed in the Senate to convict and remove an official from office.
Mr. Nadler, Ms. Pelosi and other party elders believe Mr. Trump is threatening the country’s democratic institutions. Privately, many harbor suspicions that he obstructed justice, collaborated with the Russians in 2016 or both. But they also argue that an impeachment that does not have a reasonable shot of winning a conviction in the Senate will backfire and strengthen Mr. Trump in the 2020 campaign. In the meantime, they are planning to open multiple investigations into accusations of wrongdoing around the president, his campaign and his administration.
“We shouldn’t be impeaching for a political reason, and we shouldn’t avoid impeachment for a political reason,” Ms. Pelosi said. “So we’ll just have to see how it comes.”
Republicans ignored the distinction.
“Is this the behavior that we are going to find with this new majority party in Congress?” Representative Kevin McCarthy of California, the Republican leader, asked at a news conference. He repeatedly singled out Ms. Pelosi, asking why she had not censured Ms. Tlaib.
Mr. Trump was similarly critical of Ms. Tlaib.
“I thought her comments were disgraceful,” Mr. Trump said at the news conference. “I think she dishonored herself, and I think she dishonored her family.” He added that her comments were “disrespectful to the United States of America.”
Ms. Tlaib is far from alone among House Democrats. Representatives Brad Sherman of California and Al Green of Texas formally introduced an article of impeachment on Thursday, charging that Mr. Trump had obstructed justice in firing James B. Comey, the F.B.I. director. Others are expected to follow.
“I continue to believe that obstruction of justice is the clearest, simplest and most provable high crime and misdemeanor committed by Donald J. Trump,” Mr. Sherman said in a statement. “I hope that the articles of impeachment are the subject of hearings before the Judiciary Committee early in 2019.”