WASHINGTON — Representative Justin Amash, an iconoclastic Republican of Michigan who has considered a run against President Trump in 2020, became the first member of his party serving in Congress to publicly suggest that the president’s conduct had reached the “threshold of impeachment.”
Mr. Amash, 39, used Mr. Trump’s favorite medium — Twitter — to join a groundswell of Democrats who have concluded that the president’s behavior, including instances of potential obstruction of justice laid out in the report by the special counsel, Robert S. Mueller III, meets the constitutional threshold of high crimes and misdemeanors.
Contrary to the public statements and summaries offered by Attorney General William P. Barr, “Mueller’s report reveals that President Trump engaged in specific actions and a pattern of behavior that meet the threshold for impeachment,” wrote Mr. Amash, who has been one of the president’s most outspoken Republican critics.
“In fact, Mueller’s report identifies multiple examples of conduct satisfying all the elements of obstruction of justice, and undoubtedly any person who is not the president of the United States would be indicted based on such evidence,” he added.
Mr. Amash also criticized his fellow lawmakers, writing, “Few members of Congress even read Mueller’s report; their minds were made up based on partisan affiliation.”
A White House spokesman did not immediately return a request for comment.
Mr. Amash’s statement is likely to complicate his political future: A few hours after his tweets, Jim Lower, a conservative state representative, suggested he might run against Mr. Amash next year.
“This cannot go unchallenged!” Mr. Lower tweeted. Referring to the Third Congressional District, which Mr. Amash represents, Mr. Lower continued, “I support @realDonaldTrump, I support West Michigan values, I support our party’s values and I will have a major announcement regarding MI CD3 this week!”
Mr. Amash’s conclusions track closely with those of many Democrats. While Speaker Nancy Pelosi has sought to block attempts to impeach Mr. Trump based on the findings of the Mueller report, she declared her openness last week to initiating an impeachment inquiry as a means of forcing administration officials to comply with the subpoenas of the six House committees investigating Mr. Trump’s conduct.
Earlier on Saturday, Representative Jamie Raskin, Democrat of Maryland, who serves on the House Judiciary Committee, said that an increasing number of his colleagues were moving toward a conclusion that some kind of impeachment proceeding was inevitable.
“We have to keep this in proportion with everything else we’re doing, but believe me, the anger and frustration is growing, not just in the public, but within the ranks of Democrats, too,” he said during an interview on MSNBC. “I believe that we are headed toward an impeachment inquiry.”
This is not the first time Mr. Amash, who considers himself a libertarian and strict constitutionalist, has defied the White House and bucked his party’s Capitol Hill leadership. Mr. Amash was one of 14 Republicans to side with Democrats in their unsuccessful attempt to override the president’s first veto, which upheld an emergency declaration to divert funding from other federal projects to build a wall along the southwestern border.
Republican leaders in both chambers have griped privately about Mr. Trump’s behavior but have publicly fallen in line behind the president. Mr. Trump has seized on Mr. Mueller’s finding that his campaign did not coordinate with Russia to declare that the investigation was an exoneration. (In fact, the report stopped short of clearing the president on the question of whether he illegally obstructed justice.)
On Thursday, Ms. Pelosi said she would consider impeachment only as a means of compelling Mr. Barr and Donald F. McGahn II, the former White House counsel who cooperated extensively with the special counsel’s inquiry, to testify — despite Mr. Trump’s blanket call for current and former aides to stonewall all requests by Democrats for testimony or documents.
But first, she added, House committees must exhaust all their legal and legislative options. “First we ask, then we subpoena friendly,” she said. “Then we subpoena otherwise, and then we see what we get. So let’s not leapfrog over what we think should be the path that should be taken.”
Few Republicans, especially House members like Mr. Amash who face re-election every two years, have been willing to confront Mr. Trump publicly. Former Representative Mark Sanford of South Carolina has repeatedly criticized the president and questioned his conduct — and his party’s acquiescence to him.
“The idea of some allegiance not to the Constitution, but to the president, was not what I signed up for,” Mr. Sanford told The Washington Post last year.
Over the summer, Mr. Sanford lost the Republican primary race to a Trump ally, Katie Arrington, hours after Mr. Trump called him “very unhelpful to me in my campaign to MAGA.”