Hart said Ryan was especially interested in Austrian economist Friedrich Hayek’s arguments for free market capitalism. Ryan clearly had an interest in politics, said Hart, who recommended Ryan for an internship in the office of then-Wisconsin Republican Sen. Bob Kasten. Ryan soon went to work as a speechwriter for Empower America, a conservative research center that included the late Rep. Jack Kemp, a New York Republican and former NFL quarterback who championed tax cuts as a central tenet of economic growth and whom Ryan has called a major influence.

Ryan also worked as a Republican congressional staffer before running for the U.S. House of Representatives in 1998 at the age of 28, winning the seat with the help of connections in Washington, D.C., and Wisconsin. He’s been in Congress ever since. Including his time as a staffer and with Empower America, he’s spent nearly half his life in the Washington sphere.

Ryan rose through the ranks over more experienced Republicans after the 2006 election to win the top Republican position on the Budget Committee. Idaho Republican Rep. Mike Simpson, who joined Congress at the same time as Ryan, said Ryan’s command of budget details and his personality gained him influence among House Republicans.

“Paul is a likable guy,” Simpson, who’s also on the Budget Committee, said Saturday in an interview, “He doesn’t belittle those who disagree with him. I’ve never seen him be harsh.”

Ryan, who once moonlighted as a fitness trainer at Washington Sport and Health Club, is known for his punishing morning workouts.

His ascendancy to his role as the policy voice of House Republicans began in 2008, when he issued what he called the Roadmap for America’s Future.

The budget plan’s reception wasn’t always smooth. Republicans in and out of Congress at times resisted Ryan’s push to overhaul entitlement programs such as Medicare. Newt Gingrich last year described Ryan’s Medicare proposal as “right-wing social engineering,” a comment he later disavowed.

But with the help of conservative media and think tanks Ryan began to gain traction, and Republicans who were looking for an alternative to President Barack Obama’s policies increasingly pointed to him.

Democrats said Saturday that they relished taking on Ryan. Maryland Rep. Chris Van Hollen, the top Democrat on the Budget Committee, said in a statement that Ryan’s push on Medicare and his support to keep the Bush-era tax cuts for wealthier Americans showed that Romney was “doubling down” on an agenda that favored the rich over the middle class and senior citizens.

But Republicans said the nation was in debt, entitlement changes needed to be made and Ryan was the perfect person to defend his own plan. Influential conservative publications urged Romney to choose Ryan as running mate over what were considered safer picks.

Although Ryan is a conservative star, a recent CNN poll found that 54 percent of the public said they didn’t know him or had no opinion about him. Ryan set about introducing himself to the nation Saturday at a campaign rally, and he did it in sweeping terms, not talking about a Medicare overhaul or his budget proposals.

“I represent a part of America that includes inner cities, rural areas, suburbs and factory towns. Over the years I have seen and heard a lot from families, from those running small businesses and from people who are in need. But what I have heard lately troubles me the most,” Ryan said, appearing at ease in his new role as vice-presidential choice. “There is something different in their voice and in their words. What I hear from them are diminished dreams, lowered expectations, uncertain futures.”