"Saying no is easy, leading is hard, but that is what we were elected to do," the Texas lawmaker said in a statement. "Leaving this caucus will allow me to be a more effective member of Congress."
Mr Poe was in favor of the Republican legislation, but the Freedom Caucus argued the proposal did not go far enough in repealing the 2010 Affordable Care Act, popularly known as Obamacare.
The Freedom Caucus, consisting of the House of Representatives' most conservative members, was instrumental in dealing Mr Trump a stunning political setback on Friday when Republican House leaders pulled the healthcare legislation, derailing a major 2016 election campaign promise of the president and his allies.
Mr Trump's fellow Republicans control both houses of Congress.
In a tweet on Sunday morning, Mr Trump lashed out at both the Freedom Caucus and other conservatives, saying their actions had left "Democrats smiling in DC"
(Reporting by Jason Lange, Editing by Peter Cooney)
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