Rep. Justin Amash, a critic of President Trump who entertained a run against him in 2020, became the first Republican congressman to say the president “engaged in impeachable conduct.”

The Michigan lawmaker, often the lone Trump dissenter on his side of the aisle, shared his conclusions in a lengthy Twitter thread after reviewing the full special counsel report.

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

“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 wrote.

The White House did not immediately respond to request for comment.

The president often says the report found “no collusion, no obstruction,” though neither is true. Mueller did not establish a conspiracy between the Trump campaign and Russia, which did interfere in the 2016 election. He did not rule on the obstruction of justice question, saying it was something Congress should determine.

Amash wrote that it’s partisanship keeping Republicans from exercising its checks and balances role.

“When loyalty to a political party or to an individual trumps loyalty to the Constitution, the Rule of Law-the foundation of liberty-crumbles,” he wrote.

Amash, a libertarian, considers himself a strict constitutionalist and in February was the lone Republican to join a Democratic bill to stop Trump from declaring a national emergency to fund his border wall.

“From the time the president was elected, I was urging them to remain independent and to be willing to push back against the president where they thought he was wrong,” Amash told CNN in March. “They’ve decided to stick with the president time and again, even where they disagree with him privately.”