In tapping Wisconsin Congressman Paul Ryan to be his vice presidential running-mate, Mitt Romney has chosen an ambitious, self-described "young gun" who has staked his entire career on a single issue -- slashing the federal budget.
Ryan, 42, has spent most of his adult life in Congress, with little business or executive experience to speak of.
He steadily built his credibility as a Washington insider, starting as an intern on Capitol Hill and then becoming an aide to a Republican senator from Wisconsin.
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For the past 14 years, Ryan has served as a member of the House of Representatives.
But it was his 2010 manifesto "Young Guns, A New Generation of Conservative Leaders" that elevated Ryan's prominence.
The document, which he co-authored, showcased the small government, "opportunity society" that he had been advocating for years to smaller audiences.
It provided a national forum for promoting Ryan's political agenda and made him a favorite of the anti-tax, limited-government Tea Party movement.
The manifesto also previewed the course he would steer when he became the chairman of the House Budget Committee in January, 2011, after his party scored historic gains in the 2010 elections and wrested control of the House from Democrats.
Ryan's budget-slashing agenda is one that Republican presidential candidate Mitt Romney hopes will take him and Ryan to the White House in November's elections, spurred by voter anger over a stubbornly weak U.S. economy.
Ryan also adds personal appeal to the Republican ticket.
A Green Bay Packers football fanatic, Ryan often makes reference to his Midwestern roots and how he prioritizes spending time in Wisconsin with his wife, Janna Little, a tax attorney, and their three young children.
Ryan is also a fitness buff -- his father and grandfather both died of heart attacks in their 50s -- and leads his fellow lawmakers in what has been described as a grueling daily exercise group.