The most powerful Republican in the US Congress, House Speaker Paul Ryan, said Wednesday he will not seek re-election in November, in a blow to President Donald Trump's party as it faces a bruising fight in midterm elections.
Ryan, who is second in line to the presidency, said he would serve as speaker through the November elections and into early January, the end of his term.
"This is a job that does not last forever," Ryan told reporters.
"I am announcing that this year will be my last one as member of the House."
The 48-year-old Wisconsin Republican only reluctantly assumed the House speakership in 2015 and never fully embraced Trump.
But he said his decision to retire was driven by a desire to spend more time with his family and not by the turmoil in White House.
"What I realize is if I am here for one more term my kids will only have a weekend dad. I just can't let that happen," he said.
Trump paid tribute to Ryan as "a truly good man."
"While he will not be seeking re-election, he will leave a legacy of achievement that nobody can question. We are with you Paul!" the president tweeted.
Ryan, a fiscal conservative who ran for vice president in 2012 on Mitt Romney's ticket, gave no hint of his future political ambitions.
His most important achievement as speaker was passage in December of a major tax overhaul that included steep cuts in corporate taxes.
Rumors about his departure have swirled for months in Washington, where earlier this year the talk of his retirement grew so loud that the speaker publicly knocked down the reports.
But at the time he also said that, after 20 years in Congress, he would sit down with his wife later this year to map out their future.
For his part Ryan insisted he was confident he was "leaving this majority in good hands with a very bright future."
But his departure, at a time of upheaval in the administration, only highlights the disarray within the Republican Party as it faces a crucial election test in just over six months.
The party, deeply fractured between conservatives and moderates, has been described as ungovernable. And Trump's presidency has raised questions about the role of traditional conservatism in the Republican world.
Ryan's announcement is certain to set off a major succession battle.
Democrats are fighting to flip the House, a difficult prospect in any election year, but one which experts have described as increasingly possible.
The number two Republican, House Majority Leader Kevin McCarthy, is a frontrunner for the speaker's job, should the party maintain its majority.
But with the caucus deeply fractured between conservatives and moderates, McCarthy will no doubt face competition.
Number three Republican Steve Scalise, a Louisiana conservative, has also reportedly signalled he has his eye on the speakership.
Chuck Schumer, the top Democrat in the US Senate, praised Ryan as "a good man who is always true to his word."
He expressed hope that in his remaining time in Congress, Ryan would "break free from the hard-right factions of his caucus that have kept Congress from getting real things done.
"If he's willing to reach across the aisle, he'll find Democrats willing and eager to work with him."
But there was also sniping from the Democratic side.
"With his retirement announcement, Speaker Paul Ryan becomes the first casualty of the 2018 midterm election," tweeted House Democrat Gerry Connolly.