Profile: Paul Ryan, Speaker of the House
Paul Ryan's election to Speaker of the House in October 2015 elevated the Wisconsin representative and one-time vice-presidential candidate to the top Republican spot in Congress - and in direct conflict with President Barack Obama and the conservative wing of his party.
Shortly after John Boehner announced he would be stepping down as speaker, hounded by the right-wing of the party, Mr Ryan was among those who said they wouldn't be making a bid for the top job.
But weeks later, the former chairman of the House Budget Committee changed his mind and said he would consider it if the party united behind him.
Fast forward to April 2016. After six months of brutal Republican campaigning to win the party's ticket to run for president, Paul Ryan is again poised to say he does not want a job - this time the presidential nominee.
Donald Trump continues to lead the Republican race, but many of his enemies within the party have been desperately trying to keep him short of a majority of delegates - and stop him for good at a contested convention.
With his main opponent, Ted Cruz, also unpopular among many in the party, Paul Ryan had become a possible candidate of compromise.
But Mr Ryan has repeatedly said he has no intention of becoming the nominee.
He has also said he will support whoever is nominated, despite frequent criticism of Mr Trump.
But as an analysis in the New York Times points out, he has also been developing a "parallel policy campaign" - trying to set out a platform for the party if it is splintered by the Trump-Cruz battle.
Mr Ryan was born and reared in small-town Janesville, Wisconsin, the son of a lawyer.
He cites the experience of losing his father at the age of 16 - the third generation of Ryan men 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.
He spent almost his entire career working in Washington, beginning as an ambitious and energetic Senate staff member. Mr Ryan, now 45, was first elected at the age of 28 from the same constituency he represents now.
In recent years, Mr Ryan has emerged as a chief spokesman for a brand of ideologically charged fiscal conservatism that calls for slashing government spending to the bone while also cutting taxes.
In his previous role as chairman of the House Budget Committee, he has helped lead efforts to cut government spending, casting himself as a fiscal hawk.
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) from the federal budget over a decade by cutting food aid, education spending and health programmes for the poor and elderly, and more.
It also lowers tax rates, halving corporate income tax.
But Mr Ryan has also been the lead Republican negotiator on several last-minute budget deals between the parties and the two chambers.
While he is known primarily for his fiscal conservative policies, he also adheres to the Republican Party's strict social conservative platform.
He has voted against gay adoption, gay marriage and moves to liberalise abortion laws. In 2009 and 2011, he co-sponsored bills that would declare that life begins at conception and would grant foetuses the legal and constitutional rights of people.
He opposes gun control and voted to erect a barrier along the US border with Mexico.
He has in the past listed 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 conservatives with his ideological purity.
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.
The campaign's loss to a sitting president did not seem to hurt Mr Ryan's political capital, and he returned to his role in the House until Mr Boehner stepped down in 2015.