Republican Rep. Justin Amash has, of late, emerged as his party’s most ardent critic of his party’s president, Donald Trump. In the absence of any GOP outrage to speak of, the 39-year-old Michigan congressman has been extraordinarily outspoken in his increasingly withering critiques of Trump’s behavior as detailed in the Mueller report. Put more simply, Amash is calling Trump’s actions impeachable. On Monday, Amash took another step away from his political base, leaving the ultraconservative House Freedom Caucus that Amash himself helped found and that tracks its roots to the Tea Party movement.

The decampment comes as Amash’s public rebukes of Trump have made his membership in the conservative group, created in 2015 specifically to push centrist Republican members further to the right, increasingly awkward. Some of the Trumpiest Republicans, like Ohio Rep. Jim Jordan and North Carolina Rep. Mark Meadows, call the caucus home. “Justin Amash’s conclusions are poorly informed and fatally flawed and don’t represent the views of any of the Freedom Caucus members that I’m aware of,” Meadows told reporters last month following one of Amash’s critiques of Trump’s apparent obstruction of justice. Following Amash’s very public condemnation of Trump, the Freedom Caucus took an informal vote to exhibit its disagreement with one of its founders but didn’t move to take concrete action to expel him. This week, Amash made the break himself telling CNN, “I have the highest regard for them and they’re my close friends,” but that he “didn’t want to be a further distraction for the group.”

Amash still maintains his chairmanship of the Ron Paul–inspired House Liberty Caucus, a far less influential group with libertarian underpinnings. Amash’s departure from the Freedom Caucus raises the question of whether it is the first step in Amash’s departure from the Republican Party altogether. The four-term congressman’s outspokenness has netted him a Trumpy primary challenger in his Grand Rapids district that Amash hasn’t yet committed himself to running for reelection in. Amash has, however, acknowledged mulling a third-party presidential bid, ostensibly as an anti-Trump candidate on the right, for the Libertarian Party.