Paul Ryan, from conservative wunderkind to House speaker
Paul Ryan's retirement from Congress, just months before the all-important midterm elections, leaves Republicans with a chronic political migraine.
The House of Representatives Speaker's exit will deprive the party of a star fundraiser and clean-cut family man who is as at ease schmoozing mega-donors as he is glad-handing on the front porches of the American heartland.
The Wisconsin congressman and one-time vice-presidential candidate said he was leaving to spend more time with his three teenage children.
But many pundits suspect the 48-year-old wunderkind will be unable to resist the opportunity of one day running for a higher office.
After all, some Republicans openly hoped that Mr Ryan would launch a surprise bid for the presidency in 2016 to rid them of Donald Trump.
Mr Ryan is a man in much demand - in 2015, as chairman of the Ways and Means Committee, conservative admirers all but drafted him as speaker.
He is said to have found his job frustrating, partly because of President Trump.
But Mr Ryan regards the US tax code overhaul that he shepherded last year through the lower chamber as the capstone of his legislative career.
He was born and reared in small-town Janesville, Wisconsin, the son of a lawyer.
Mr Ryan cites the experience of losing his father at the age of 16 - the third generation of his family to die in their 50s - as helping to build his belief in self-reliance.
He is married to tax lawyer Janna Little. The couple have three children and still live in Janesville.
Mr Ryan has spent almost his entire career working in Washington, beginning as an ambitious and energetic Senate staff member.
He was first elected in 1999 at the age of 28 from the same constituency he represents now.
Mr Ryan presents himself as a fiscal conservative, and he championed efforts to cut government spending in his previous role as House Budget Committee chairman.
He is best known for his controversial alternative budget framework, produced to counter President Obama's budgets in 2011 and 2012, which he titled the Path to Prosperity.
The plan suggested $6tn (£3.8tn) be slashed from the federal budget over a decade by cutting food aid, education spending and health programmes for the poor and elderly, and more.
Mr Ryan has also been the lead Republican negotiator on several last-minute budget deals between the parties and the two chambers.
He supports, too, the Republican party's strict social conservative platform, having voted against gay adoption, gay marriage and moves to liberalise abortion laws.
Mr Ryan opposes gun control and voted in support of Donald Trump's plan for a wall along the US border with Mexico.
He has in the past listed conservative heroine Ayn Rand as a strong personal influence, reportedly saying the US writer's work - which praises individualism over altruism - was required reading for his staff.
But he has broken from conservative orthodoxy in the past, both in his political career and his personal life, complicating his effort to woo conservative purists.
He voted for President George Bush Jr's drug programme for senior citizens, a massive public entitlement designed without a guaranteed funding stream. In late 2008, he voted for the bank bailout.
He was accused of hypocrisy after acknowledging that his office lobbied for federal stimulus money in 2009, despite his earlier denials.
But Mr Ryan's appeal to conservative, Tea Party voters was strong enough that Republican nominee Mitt Romney chose him as his running mate for the 2012 election.
All of Washington - especially Donald Trump - will be watching his next move like hawks.