Sen. Rand Paul (R-KY) on Wednesday said he disagrees with Rep. Justin Amash’s (R-MI) remarks concerning President Donald Trump and impeachment, stating that special counsel Robert Mueller’s investigation into now-debunked collusion between the Trump campaign and Russia in the 2016 presidential election was the “antithesis of libertarianism.”

“I actually think the libertarian position on the investigation is ― you know, libertarians, we’ve been very, very critical of the intelligence community having too much power, including congressman Amash has said, you know, really you should have to get a warrant before you get an American’s records,” Paul said in an interview with the Huffington Post.

Amash, a libertarian-leaning congressman often at odds with his fellow Republicans, is facing blowback after accusing President Donald Trump on Saturday of engaging in “impeachable” conduct and claiming Attorney General William Barr mischaracterized 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 meets the threshold for impeachment,” Amash wrote in a series of tweets. The lawmaker then argued that 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.”

Contrary to Amash’s comments, Mueller found no collusion between the Trump campaign and Russia during the election, while attorney general and Deputy Attorney General Rod Rosenstein determined that the president did not obstruct justice.

Leading Republicans, including President Donald Trump and House Minority Leader Kevin McCarthy (R-CA), have hit back at Amash’s remarks, calling the Michigan congressman a “lightweight” and an attention seeker.

On Monday, the House Freedom Caucus evening voted to condemn Amash, one of the group’s founding members, over his recent remarks. House Oversight Committee ranking member Jim Jordan (R-OH), who previously served as chairman of the Freedom Caucus, said that all 30 members in attendance at the caucus’s weekly meeting voted for the measure.

In addition to facing rebuke from his colleagues, Amash’s remarks have earned him a primary challenge.

Michigan State Rep. Jim Lower (R) announced Monday he will mount a primary challenge to Amash. Lower was expected to officially launch his campaign around July 4th but moved up the announcement after the congressman’s comment.

“Congressman Justin Amash tweets yesterday calling for President Trump’s impeachment show how out of touch he is with the truth and how out of touch he is with people he represents,” said Lower. “He must be replaced and I am going to do it.”