Michigan Congressmember Justin Amash broke with his party to become the first Republican lawmaker to publicly say President Trump engaged in “impeachable conduct” in the wake of last month’s Mueller report. In a lengthy tweet thread Saturday, Amash accused Attorney General William Barr of “deliberately misrepresent[ing]” the special counsel’s report. He also wrote that “Partisanship has eroded our system of checks and balances” and that “Few members of Congress have read the report.”

Trump lashed out at Amash on Twitter, calling him a loser and writing, “Never a fan of @justinamash, 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.”