WASHINGTON — Rep. Justin Amash's weekend statement that he believes President Donald Trump has committed impeachable offenses sparked mounting GOP criticism Monday of the Michigan congressman's position — and questions about his political future.

“Justin’s a friend, but Justin is wrong on this, clearly, and the way he did this is all wrong as well,” said Amash’s fellow Freedom Caucus peer, Rep. Andy Biggs, R-Ariz., in an interview Monday on Fox News.

House Minority Leader Kevin McCarthy, R-Calif., said Sunday that he believes his GOP colleague is only seeking attention.

“This is exactly what you would expect from Justin. He never supported the president. And I think he's just looking for attention,” McCarthy said in an interview on Fox News. “ I think he's only ever asked one question in all the committees that he's been in. He votes more with Nancy Pelosi than he ever votes with me. It's a question whether he's even in our Republican Conference as a whole.”

House Minority Whip Steve Scalise, R-La., told reporters on Capitol Hill Tuesday that Amash was "dead wrong" and that his reading of the Mueller report is "just off base."

Trump, meanwhile, dismissed Amash on Sunday, calling him a “total lightweight” and a “loser who sadly plays right into our opponents hands!”

He continued the attack on Monday. "He probably wants to run for some other office," Trump told reporters outside the White House. "He’s been a loser for a very long time."

Back home, some of his constituents also had tough words for their congressman, the first GOP member of Congress to argue that Trump has committed impeachable offenses, with several raising questions about his political future — and at least one potential rival citing the comments to launch a primary challenge.

In a series of Saturday tweets, Amash said that after reading special counsel Robert Mueller’s redacted report on Russia’s interference in the 2016 election “carefully and completely,” and further review, he had concluded that, among other things, “Trump engaged in specific actions and a pattern of behavior that meet the threshold for impeachment.”

Some of his constituents disagreed. “I think he’s wrong,” GOP voter Dustin Lienau told MSNBC Monday at The Pancake House in Battle Creek, Michigan, part of the state’s 3rd Congressional District, adding he could “very well” vote against Amash next year as a result of his position on impeachment.

Virginia Wolfe, a former Democrat, said Monday that Amash was free to say what he believed — she just didn't happen to agree, and planned to vote against him.

“If that’s what he believes, then you need to stand up for what you believe. OK? I’m OK with him doing that, just my belief is I don’t agree with him,” she said. “Anybody can do what they want, anybody has the right to stand up for what they believe, but my opinion — I just think they need to let [Trump] do his job and things that happened in the past are in the past."

On Monday, Amash’s first official 2020 GOP primary challenger — Michigan state Rep. Jim Lower, who said in a statement that he is a “pro-Trump, pro-life, pro-jobs, pro-2nd Amendment, pro-family values Republican” — said that the congressman's remarks “show how out of touch he is with the truth, and how out of touch he is with people he represents.”

Amash continued to defend his stance Monday, tweeting that the "high Crimes and Misdemeanors" which can serve as grounds for impeachment do "not require corresponding statutory charges. The context implies conduct that violates the public trust."

People who say there were no underlying crimes and therefore the president could not have intended to illegally obstruct the investigation—and therefore cannot be impeached—are resting their argument on several falsehoods: — Justin Amash (@justinamash) May 20, 2019

Amash, 39, who identifies as a libertarian Republican, is considered among the most conservative members of the House, which he’s served in since 2011. Conservative groups like the Club for Growth, Heritage Action for America and Americans for Prosperity have awarded him lifetime ratings of more than 85 percent.

Despite his record, Amash is often viewed as an outlier within his own conference.

In February, he was one of 13 Republicans to join 232 Democrats in favor of a bill to overturn Trump’s emergency declaration to build a border wall. A month later, he defected again and joined Democrats in a vote to override the president’s veto of that measure. And in December, Amash was one of only eight Republicans to vote against a spending bill that would have provided $5.7 billion in border wall funding. According to FiveThirtyEight, Amash voted about 54 percent of the time with Trump in the first two years of his presidential term.

And he went further than most Democrats are willing to go publicly in his argument outlining the case for Trump’s impeachment — including Pelosi, D-Calif., who as speaker has so far mainly laid out the case against currently pursuing impeachment.

The president’s allies have long questioned Amash’s loyalty to the party, with senior White House aide Dan Scavino tweeting in April 2017 that the congressman was a “big liability” and urged people to “defeat him in primary.”

And Amash has suggested for nearly as long that he would not rule out impeachment. He told reporters in May 2017 that if former FBI Director James Comey’s assertion that Trump pressured him to end the investigation into former national security adviser Michael Flynn were true, it would be grounds for impeachment.

While he hasn't been the only Republican lawmaker to speak critically of the president, that group has dwindled drastically in the new Congress, with the resignation, retirement or defeat of former GOP members such as Reps. Charlie Dent and Ryan Costello, both of Pennsylvania, and Mark Sanford of South Carolina, and Sen. Jeff Flake of Arizona.

And his new position finds Amash standing alone.

Sen. Mitt Romney, R-Utah, who has often made critical statements about the president, said that while Amash’s statement was “courageous,” there isn’t enough evidence in the Mueller report to make a case that Trump obstructed justice.

“I also believe that an impeachment call is not only something that relates to the law, but also considers practicality and politics,” Romney said Sunday on CNN. “And the American people just aren't there. And I think those that are considering impeachment have to look also at the jury, which would be the Senate. The Senate is certainly not there either.”

An Amash voter back in his district Monday, Bob Burgett, said that he likes Trump and disagrees with Amash’s position, but it won’t dissuade him from backing him.

“I still stand with Amash because like I said I like his honesty. I don’t always agree with him, but he’s honest and that’s what I like,” he said. “I want someone who if you’re going to serve the people, I want him to be honest.”

Brewster and Puskar reported from Battle Creek, Mich.