WASHINGTON — President Trump on Sunday lashed out at Rep. Justin Amash, calling him a “total lightweight” and “loser” one day after the Michigan Republican said Trump’s conduct meets the threshold for impeachment.

Amash is the first Republican member of Congress to say the president “engaged in impeachable conduct.”

In morning tweets, Trump said he was “never a fan” of Amash, “a total lightweight who opposes me and some of our great Republican ideas and policies just for the sake of getting his name out there through controversy.”

The president argued that special counsel Robert Mueller III’s report on Russian interference in the 2016 election was “biased” but that it was “nevertheless strong on NO COLLUSION and, ultimately, NO OBSTRUCTION.”

Mueller found 10 “episodes” of potential obstruction of justice by Trump but ultimately concluded that it was not his decision to determine whether the president broke the law.

Attorney General William Barr said he had reviewed the evidence and found it insufficient to support an obstruction charge.

In the report, Mueller’s team also wrote that while the investigation established that the Trump campaign “expected it would benefit electorally from” information stolen in Russia-backed efforts, it “did not establish that members of the Trump campaign conspired or coordinated with the Russian government in its election interference activities.”

Trump added on Sunday, “Anyway, how do you Obstruct when there is no crime and, in fact, the crimes were committed by the other side?”

“Justin is a loser who sadly plays right into our opponents hands!” he said.

Amash’s office did not immediately respond to a request for comment.

Republican leaders on Sunday joined Trump in criticizing Amash. House Minority Leader Kevin McCarthy, R-Calif., called Amash’s comments “very disturbing,” arguing that the lawmaker is “not a criminal attorney. He’s never met Mueller. He’s never met Barr.”

“Those who know Justin Amash, this is exactly what he wants. He wants to have attention,” McCarthy said in an interview on Fox News Channel’s “Sunday Morning Futures.”

McCarthy also took aim at Amash’s record as a lawmaker.”I think he’s only asked one question in all the committees he’s been in,” McCarthy said. “He votes more with (House Speaker) Nancy Pelosi than he ever votes with me.”

During one February hearing alone, Amash asked several questions of former Trump personal attorney Michael Cohen, including, “What is the truth President Trump is most afraid of people knowing?”And despite McCarthy’s claim about Amash’s voting record, the Michigan Republican has a 68 percent conservative rating, according to 2015 rankings by the Almanac of American Politics.

Sen. Mitt Romney, R-Utah, said Sunday that he respects Amash and believes he made a “courageous statement” about his views on impeachment. But Romney noted that he had come to a different conclusion.

“As I read the report, I was troubled by it,” he said on CNN’s “State of the Union.” “It was very disappointing, for a number of reasons. But it did not suggest to me that this was time to call for impeachment.”

Romney added that “when there’s not an underlying crime, I think it’s difficult to put together an effective case to prosecute for those crimes.”

Amash, a libertarian, considers himself a strict constitutionalist and is often the lone Trump dissenter on his side of the House aisle.

After reviewing the Mueller report, he shared his conclusions in a lengthy Twitter thread on Saturday.

Amash wrote that after reading the 448-page report, he had concluded that not only did Mueller’s team show that Trump had attempted to obstruct justice but that Barr had “deliberately misrepresented” the findings. Amash added that “few members of Congress even read Mueller’s report.”

“Contrary to Barr’s portrayal, Mueller’s report reveals that President Trump engaged in specific actions and a pattern of behavior that meet the threshold for impeachment,” Amash said.

Some Democrats on Sunday pointed to the Amash pronouncement as meeting one of the main conditions that Pelosi, D-Calif., set for beginning impeachment proceedings – her mandate that some Republicans support such a step.

“There is now bipartisan support,” Rep. Pramila Jayapal, D-Wash., said on “State of the Union.”

Pelosi has been openly opposed to starting impeachment proceedings because public sentiment has been against it, and until Saturday, no Republican in Congress had indicated anything close to support for removing Trump from office.

“Impeachment is so divisive to the country that unless there’s something so compelling and overwhelming and bipartisan, I don’t think we should go down that path, because it divides the country. And he’s just not worth it,” Pelosi told The Washington Post in a March interview, her most detailed comments on impeachment.

On Sunday, Jayapal called Amash’s statement a “watershed moment.”Jayapal, one of the co-chairs of the Congressional Progressive Caucus, said the push now would be to just begin formal proceedings in the House Judiciary Committee. That, she said, will give Democrats better legal standing in federal courts to defeat Trump’s assertion of executive privilege in not turning over more details from the Mueller report and blocking testimony from former White House officials.

“We are very quickly headed down that path,” Jayapal said of starting impeachment proceedings.

Rep. Adam B. Schiff, D-Calif., chairman of the House Intelligence Committee, also praised Amash, saying he has shown “more courage than any other Republican in the House or Senate.”

Schiff added there is a growing sense among lawmakers that beginning impeachment proceedings may be the best strategy to combat the Trump administration’s “maximum-obstructionism campaign against Congress.”

There is “an increasing number of Democrats, and maybe Republicans, who feel this president’s conduct is so incompatible with the office … that if the only way that we can do our oversight is through an impeachment proceeding, then maybe we have to go down that road,” Schiff said on CBS News’ “Face the Nation.”