"Today, I am declaring my independence and leaving the Republican Party." 

Rep. Justin Amash, who represents Michigan's Third Congressional District in the U.S. House of Representatives and only congressional Republican to publicly argue that President Donald Trump has engaged in impeachable conduct, has announced he is quitting the GOP. 

The announcement was made in an op-ed in the Washington Post Thursday morning.

"No matter your circumstance, I’m asking you to join me in rejecting the partisan loyalties and rhetoric that divide and dehumanize us," Amash wrote. "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."

RELATED: Republican Rep. Justin Amash: Trump has 'engaged in impeachable conduct'

Amash did not mention the President by name in the op-ed, but the move to leave the GOP comes after months of backlash from the President and Amash's colleagues after his comments about Trump's conduct as detailed in the Mueller report. 

President Trump took to Twitter Thursday, calling Amash "one of the dumbest and most disloyal men in Congress." 

Amash walked in East Grand Rapids' Hollyhock Parade just hours after his op-ed was published. 

"As Independence Day grew nearer, it seemed like the right thing do. But I've been thinking about it for a little while" he said. "I've been in party politics for several years now, and the parties are voting based on partisan instincts rather than principles. And I think that's the wrong thing to do." 

Supporters of Amash at the parade described the move as "poetic" and "poignant." 

"I think regardless of your political affiliation, there's at least a vote and a voice of independence and fresh thinking," said Michael Terhorst. 

Another voter, Amy Genthe, said Amash is standing up for "true American ideals." 

However, not everyone is in support of the congressman's decision. 

"He changed," said Karla Anderson. "I'm not against him. I'm just going to vote for somebody that has the same ideals that I do. Because, I love America." 

RELATED: All by himself: Amash alone among GOP on impeachment
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Since mid-May, Amash has been in the spotlight after he published a 13-tweet thread that explained his conclusions on the Mueller report. The Republican representative said he read the whole report, and from what the Russia probe found, "President Trump has engaged in impeachable conduct."

Amash left the House Freedom Caucus, a group he helped establish in 2015, in June, saying he didn't want to be a "further distraction for the group." 

RELATED: Five Michigan representatives support impeachment inquiry

Amash is often described as Libertarian and detailed in his op-ed, "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."

He wrote that in recent years, he's become "disenchanted with party politics" and frightened by what he's seen. "The two-party system has evolved into an existential threat to American principles and institutions."

In the last few weeks, a number of Republican challengers have announced plans to run against  Amash, who has represented Michigan's Third Congressional District since 2010. Most recently Peter Meijer, of the well-known Meijer family, announced his entry in the race Wednesday, July 3. Also bidding for Michigan's Third Congressional District is State Rep. Lynn Afendoulis. She announced her candidacy on June 27.

"I'm feeling really good," Afendoulis said at the parade. "I'm feeling confident."

State Rep. Jim Lower from Greenville is also in the running, as well as military veteran Tom Norton. Norton said Amash does not care about the United States that much, saying the congressman perceives himself as an "icon." 

For weeks Amash has been asked repeatedly if he is considering a run for president as an independent. The Congressman's response is always the same: he hasn't ruled it out. 

But on Thursday, he confirmed that he will be running as an independent for Congress. 

"I'm focused on representing this community and defending the Constitution," he said.  

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