WASHINGTON (AFP) - US House Speaker Paul Ryan's shock retirement announcement marks the latest victory in a populist, anti-establishment revolution that brought its champion Mr Donald Trump to power and is remaking the Republican Party.
Whether that spells long-term GOP success in policy-making, diplomacy and at the ballot box remains unclear. Trumpism is ascendant in Washington, but is a permanent Republican shift away from conservative orthodoxy and the establishment underway - or is the party makeover temporary?
Mr Ryan, 48, is the traditional conservative who over a two-decade political career came to symbolise Republican power on Capitol Hill.
But if Mr Ryan had the party in his hands, Mr Donald Trump pulled it away.
A wonkish budget hawk early on, Mr Ryan chaired the all-important Ways and Means Committee, was plucked as the party's vice presidential nominee in 2012, and rose to become speaker in 2015, in part to serve as a bridge between feuding moderates and tea party conservatives.
His announced departure after just 30 months as the most powerful Republican in Congress suggests that what once belonged to establishment Republicans - those buoyed by the conservative revolution of Mr Ronald Reagan - is now up for grabs.
"It's no longer firmly in their control," history professor Michelle Nickerson, of Loyola University in Chicago, told AFP.
"And I think that with the departure of Ryan, what we're seeing is that we're not going back," she added.
"There's a willingness" to embrace populism, she added.
That theory was tested - and proven - in 2016 by political rabble-rouser Steve Bannon, who helped Mr Trump win the presidency and became his chief strategist in the White House.
And while Mr Bannon's ouster last year suggested the establishment was striking back, other signals defied that narrative.
Mr Ryan and other prominent pro-trade, inclusive lawmakers warned against Mr Trump's trade war threats and his sabre-rattling, but their concerns appear to have been swept aside.
Immigration reform has failed and "build the wall" remains a common refrain at Trump events.
Some critics see Mr Ryan as a Trump enabler, denying his own fiscal austerity convictions to lead the charge on a US$1.3 trillion (S$1.71 trillion) Trump-backed spending Bill that passed Congress last month.
In a daring speech on the Senate floor last October, Republican Senator Jeff Flake warned that the coarseness of the Trump era was becoming the "new normal" - a flash of "destructive politics" that could set the conservative cause back a generation.
Mr Flake has announced he is retiring this year, acknowledging he would not be able to win his own primary in the current anti-establishment environment.
Mr Ryan and Mr Flake join a record number of other congressional Republicans heading for the exits, retiring in part because of a potential Democratic takeover in the upcoming mid-term elections in November.
They include prominent traditionalists like Senator Bob Corker, congressmen Ed Royce, Mr Bob Goodlatte, and centrists Charlie Dent and Mr Dave Reichert.
"They're middle of the road in temperament, and I think that no matter what happens in November, that's a big brain drain and loss of experience in Congress for the Republican Party," said Dr Matthew Green, a Catholic University professor who has taught on politics in the age of Trump.
"I think we're in a really interesting zone of uncertainty," he added.
"If there are successful candidates modelling themselves after Trump, that's a sign that the party is moving in Trump's direction... November is going to be really telling."
Equally important might be who the party chooses as its new leader in the House.
Majority Leader Kevin McCarthy is the clear front-runner, and the Republican number three, Mr Steve Scalise, may also seek the gavel. Mr Trump is said to be close to both of them.
But a Republican leader built in Mr Trump's own image - a political bomb-thrower, ruled by impulse - is unlikely, Dr Green said.
"I don't see a Trump acolyte becoming speaker."
Trumpism has its work cut out to show the world it is a viable political brand that can hold its own against likely Democratic advances in November - and can survive after Mr Trump himself steps off the stage in either three or seven years.
But if change is the only constant, Trumpism itself might soon be under threat.
Dr Green, the Catholic University professor, said it is not uncommon for a party to support its President "pretty much on anything".
"Then, when he leaves the White House, they revert back."