One month after Donald Trump took his oath of office, Rep. Justin Amash (R–Mich.) pinned at the top of his very active Twitter feed George Washington's famous farewell address warning against "the baneful effects of the spirit of party generally."

This morning, not seven weeks after breaking ranks with this party in calling for impeachment proceedings against the president, Amash announced in a Washington Post op-ed that he's leaving the GOP and declaring himself an independent.

"Today, I am declaring my independence and leaving the Republican Party," the five-term congressman wrote. "No matter your circumstance, I'm asking you to join me in rejecting the partisan loyalties and rhetoric that divide and dehumanize us….The two-party system has evolved into an existential threat to American principles and institutions."

Amash, 39, had become increasingly isolated within the congressional GOP long before spelling out in a Twitter thread his conclusion that Trump "has engaged in impeachable conduct." He crossed swords with the administration on the travel ban, Obamacare repeal/replace, the firing of then–FBI director James Comey, various spending increases, tariffs, the president's relationship with Russian President Vladimir Putin, birthright citizenship, Saudi Arabia, eminent domain, and the emergency declaration along the border, for starters.

Since the impeachment apostasy, Amash has become a GOP pariah, drawing rebukes from the very House Freedom Caucus he co-founded, defections of key financial supporters, primary challengers, and freelance sniping from Michigan's congressional Republicans. "In this hyperpartisan environment," Amash lamented today, "congressional leaders use every tool to compel party members to stick with the team, dangling chairmanships, committee assignments, bill sponsorships, endorsements and campaign resources."

In a July 2017 interview with Reason (you can watch the whole thing below), the Grand Rapids native said that he preferred the descriptor "libertarian" rather than "libertarian-leaning Republican," and stated that "hopefully, over time, these two parties start to fall apart." Americans, he said, "need to move away from this idea that you just have two parties who are at war with each other, and one party is good and the other party is evil, because that leads to all sorts of bad outcomes. You get end-justifies-the-means thinking in just about everything, and liberty doesn't really have an opportunity to flourish in that sort of environment."

The congressman hit similar notes in his op-ed, quoting more extensively from Washington's speech ("one of America's most prescient addresses"), and furthering what Peter Suderman in these pages has characterized as "a critique of reflexive partisanship and a system that works from the expectations that party affiliation is the most important (and, in many cases, the only) factor that matters in high-stakes political decisions."

"Americans have allowed government officials, under assertions of expediency and party unity, to ignore the most basic tenets of our constitutional order: separation of powers, federalism and the rule of law," Amash wrote. "The result has been the consolidation of political power and the near disintegration of representative democracy."

As a result: "Instead of acting as an independent branch of government and serving as a check on the executive branch, congressional leaders of both parties expect the House and Senate to act in obedience or opposition to the president and their colleagues on a partisan basis."

It is notable that Amash is going indie, and not joining the political party whose name matches his preferred ideological descriptor. This carries both practical and rhetorical considerations.

On the practical side, the congressman will no longer be a candidate in the April 2020 Republican primary for Michigan's third congressional district; he is expected instead to file papers to run for re-election as an independent. The Amash team had previously expressed confidence in the face of early polls showing his main primary challenger 16 percentage points ahead, but now will have to make an electability case based on the power of incumbency in a three-way contest. (Michigan is a straight-ticket ballot state, which he told me in August 2018 "makes it prohibitive to run outside of the major parties.")

Amash's announcement is also sure to fuel ongoing speculation that he's readying a bid for the 2020 Libertarian Party presidential nomination, a prospect even his own would-be competitors are cheering on. The party's selection doesn't take place until May 2020, so until and unless Amash rules out a run, the next nine months will be a festival of guessing, gamesmanship, and gossip.

But in his piece today, which does not mention the president by name, the congressman is more concerned with how two-party partisans are fighting more viciously over a shrinking pie of public affiliation.

"Modern politics is trapped in a partisan death spiral, but there is an escape," he writes. "Most Americans are not rigidly partisan and do not feel well represented by either of the two major parties. In fact, the parties have become more partisan in part because they are catering to fewer people, as Americans are rejecting party affiliation in record numbers."

Perhaps mindful that his impeachment comments demonstrably moved public opinion among political independents, Amash continues: "These same independent-minded Americans, however, tend to be less politically engaged than Red Team and Blue Team activists," he writes. "Many avoid politics to focus on their own lives, while others don't want to get into the muck with the radical partisans."

And so: "I'm asking you to believe that we can do better than this two-party system—and to work toward it. If we continue to take America for granted, we will lose it."

Reason's interview with Amash from July 2017: