Florida Republican congressman Bill Posey is retiring at the end of this year.
Posey joins a wave of Republicans who are heading for the exits, with some citing the pressure of working in Washington at a deeply divisive time.
The longtime representative cited circumstances "beyond my control" for his abrupt decision, which is unlikely to impact the balance of power in Congress.
Posey's district is reliably conservative, and he has already picked out a successor, former state Senate president Mike Haridopolos.
In a statement thanking his supporters, Posey said he could stay in office "forever", but unspecified circumstances had changed his plans.
“It has been the greatest honor of Katie’s and my life to represent you in Congress," Posey wrote in his statement on Friday.
“And, polls suggest that because of YOUR support, I could remain in the job forever, and we were looking forward to another spirited campaign for a final term in office. However, earlier this week circumstances beyond my control now require me to suspend my re-election campaign."
Posey said he had been planning to run for re-election only days ago but "the stars aligned" and changed his thinking.
Posey said he will focus on helping Donald Trump take back the White House and electing Haridopolos to his congressional seat.
"Without going into a lot of personal details, stars aligned during the past week and Mike decided he was ready for Congress. I enthusiastically endorse him and will do everything I can to help him get elected," he said.
Posey was elected to represent the 8th district in 2008.
He won't be gone until the end of the year, so his retirement won't shrink the GOP's already razor-thin House majority, which has been impacted by a wave of early retirements.
The party has been convulsed by divisions, with House Speaker Mike Johnson (R-La.) facing threats of removal over his bi-partisan cooperation with Democrats, who have praised him enthusiastically for passing billions in foreign aid to Ukraine and Israel.
With some of his last votes, Posey opposed Johnson's foreign aid push and the renewal of the controversial FISA spying program.
During the Obama years, he backed legislation that would have forced presidential candidates to share their birth certificates.
