A Michigan congressman who was the first Republican to call for President Donald Trump’s impeachment defended himself Monday against attacks from other Republicans supporting Trump.

Rep. Justin Amash, a five-term member of the House of Representatives, said his critics employed “several falsehoods” in claiming that Trump did not obstruct justice by trying to thwart the lengthy investigation by special counsel Robert Mueller into Russian meddling in the 2016 U.S. presidential election.

Critics of the Mueller probe, including the president, have claimed that Trump could not obstruct justice because there was no underlying crime to obstruct since Mueller found that neither Trump nor his campaign colluded with Russia to help him win the White House.

But Amash said, and U.S. legal analysts have agreed, that obstruction of justice does not require the prosecution of an underlying crime.

“There is a logical reason for that. Prosecutors might not charge a crime precisely ‘because’ obstruction of justice denied them timely access to evidence that could lead to a prosecution,” Amash said.

He added, “There were many crimes revealed by the investigation, some of which were charged, and some of which were not.”

Trump on Sunday called Amash “a total lightweight” and “a loser who sadly plays right into our opponents hands!” by calling for Trump’s impeachment. Trump said Amash “opposes me and some of our great Republican ideas and policies just for the sake of getting his name out there through controversy.”

Congressman Kevin McCarthy, leader of the minority bloc of House Republicans, attacked Amash’s call for Trump’s impeachment, saying it was “very disturbing. …. He never supported the president, and I think he’s just looking for attention.”

Republican National Committee Chairwoman Ronna McDaniel accused Amash of “parroting the Democrats’ talking points on Russia.”

In Amash’s congressional district in the Midwestern state of Michigan, state lawmaker Jim Lower said he would run against Amash in a Republican party primary election next year because of his attack on the president. Lower called himself a “pro-Trump, pro-life, pro-jobs, pro-Second Amendment, pro-family values Republican.”

Some Democratic lawmakers in the House have called for Trump’s impeachment, although House Speaker Nancy Pelosi has not given her approval for the start of any impeachment hearings, while leaving open the possibility as several House committees conduct new investigations of Trump’s business affairs and taxes.

Trump has vowed to fight all efforts at subpoenas for information about his conduct and administration policies. Some of the disputes about access to Trump and White House records are already being fought in legal battles, with more likely to come.

Mueller concluded that Trump and his campaign did not collude with Russia to help him win the election, but it did not take a position on whether the president obstructed justice as the probe took place. Subsequently, Attorney General William Barr and Deputy Attorney General Rod Rosenstein decided obstruction charges were not warranted against Trump.

Amash, after reading the Mueller report, contended in a string of Twitter comments on Saturday that Barr “has deliberately misrepresented Mueller’s report,” saying that Barr “intended to mislead the public” about Mueller’s findings.

“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,” he continued. “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.”

A long-standing Justice Department policy says that sitting U.S. presidents cannot be charged with criminal offenses, but can be charged after they leave office.

Amash said, “Impeachment, which is a special form of indictment, does not even require probable cause that a crime (e.g., obstruction of justice) has been committed; it simply requires a finding that an official has engaged in careless, abusive, corrupt, or otherwise dishonorable conduct.”

​The congressman said that he thinks “few members of Congress” have read the Mueller report and that “their minds were made up based on partisan affiliation.”

Even if the Democratic-controlled House impeached Trump, the Republican-controlled Senate would almost certainly reject removing Trump from office.