Last month, Rep. Justin Amash left the House Freedom Caucus. Last week, he left the Republican Party. And now, he has left the Republican Conference and the House Committee on Oversight and Reform.

“Please accept this letter as formal notification that I am withdrawing my membership in the House Republican Conference, effective immediately, for the reasons outlined in my accompanying op-ed,” Amash said in his letter to Republican leaders. He also said he was resigning from the House Oversight Committee.

Amash penned an opinion piece in The Washington Post, explaining why he decided to make the move.

"My parents, both immigrants, were Republicans. I supported Republican candidates throughout my early adult life and then successfully ran for office as a Republican. The Republican Party, I believed, stood for limited government, economic freedom and individual liberty – principles that made the American Dream possible for my family," he wrote.

"In recent years, though, I've become disenchanted with party politics and frightened by what I see from it. The two-party system has evolved into an existential threat to American principles and institutions," Amash said.

The Congressman announced his formal resignation on Twitter:

Today, I sent the attached letter to Republican leaders as formal notification that I am withdrawing my membership in the House Republican Conference and, consistent with House rules, resigning from the Committee on Oversight and Reform. pic.twitter.com/8x8lFUmaGY — Justin Amash (@justinamash) July 8, 2019

Amash's announcement comes after Rep. Mark Walker (R-NC) previously called on his colleague to leave the Republican Conference after Amash denounced the Republican Party.

Amash left the @freedomcaucus now he’s leaving the @GOP. The @HouseGOP never left @justinamash - we simply ran out of space for his ego. However, we should make sure he leaves Conference and his committee. — Rep. Mark Walker (@RepMarkWalker) July 4, 2019

President Donald Trump was happy about Amash leaving the GOP.