The lone Republican calling for President Donald Trump’s impeachment has quit an influential caucus of House conservatives.

A spokeswoman for Michigan Rep. Justin Amash confirmed on Tuesday that he had resigned from the Freedom Caucus. Amash is one of the group’s founders, but it is now controlled by Trump’s allies.

Amash called for Trump’s impeachment last month based on special counsel Robert Mueller’s report on Russia’s election meddling and the president’s efforts to shut down the investigation. Mueller did not find that Trump or his allies conspired with Russia.

Amash has not said whether he will run for re-election to his Grand Rapids-area seat.

He has left open the prospect of running for president in 2020 as a Libertarian.

Here’s more from Politico:

The Michigan lawmaker told a CNN reporter that he has “the highest regard for them, and they’re my close friends,” but he “didn’t want to be a further distraction for the group.” Amash’s decision to step down was confirmed to POLITICO by his office.

Amash, a founding member of the Freedom Caucus, has long been a lone wolf in Congress, routinely bucking GOP leadership and defying Trump on a number of issues throughout the past two years.

But Amash’s support for impeachment roiled members of the Freedom Caucus, who found Amash’s criticism dead wrong. The group decided to uniformly oppose his impeachment stance last month, though they stopped short of kicking him out of the caucus — despite some lawmakers complaining that Amash was still a member.

Amash, a 39-year-old libertarian who rode the 2010 tea party wave to Congress, had stopped showing up to HFC meetings this year and even threatened to quit the group at one point last year after they didn’t stand up to Trump for attacking one of their own members, South Carolina’s Mark Sanford, who was facing a pro-Trump primary challenge.

Now, Amash finds himself in a similar position, facing two primary challenges back home and being ripped by Trump on Twitter.