The fifth-generation Wisconsin native, who marks his 41st birthday this week, enters the new Republican-controlled session of the House as chairman of the Budget Committee and the point man for the GOP drive to reduce the national debt by slashing government spending.
Well-spoken and well-liked by House colleagues, Ryan also has drawn the ire of Democrats and liberal groups because, unlike other Republicans who leave out the details in how they would cut federal spending, Ryan has never been afraid to be specific.
Sen. Bernie Sanders, a liberal independent from Vermont, applauded Republicans for picking Ryan, saying that unlike GOP leaders who have "been vague about what programs they want to cut, Congressman Ryan has been very clear." He added that Ryan's ideas on squeezing savings from Social Security, Medicare, Medicaid and other programs were "a very wrong approach to take."
During the fall election campaign, Democrats jumped on Ryan's advocacy, expressed in his proposal "A Roadmap for America's Future," of giving workers under 55 the option of investing part of their Social Security taxes in government-run personal retirement accounts. Those choosing to invest would receive a lower guaranteed Social Security benefit when they retire.
Other Republicans have been cautious about supporting this concept following the recession-led turmoil in the stock market. But GOP Majority Leader Eric Cantor, asked on NBC's "Meet the Press" Sunday about Ryan's approach to Social Security, said the roadmap was something "we need to embrace."
Ryan is outspoken in his criticism of the new health care law passed by Democrats last year. As an alternative, he has proposed giving people under 55 a refundable tax credit of $2,300 for individuals and $5,700 for joint filers to purchase health insurance. He would replace Medicaid with private insurance for most low-income people.
Ryan's profile rose last year when he joined Cantor, of Virginia, and the new Republican whip, Kevin McCarthy of California, in co-authoring the book "Young Guns, A New Generation of Conservative Leaders," that sets out their blueprint for restoring the nation's prosperity.
"Together, they are ready to make history. Together, they are the young guns," intones the promo to the book.
"Paul Ryan has spent the better part of the last two years explaining exactly why the Democratic agenda has been so bad for jobs and the economy," Senate Republican leader Mitch McConnell of Kentucky said in praising the choice of Ryan to respond to Obama's address to Congress.
Ryan was a member of the just-concluded presidential deficit commission but, like other House participants, declined to support the final recommendations made last month by its co-chairmen, Democrat Erskine Bowles and Republican Alan Simpson, because it included tax increases and didn't do enough to rein in health care costs.
But Ryan has also been able to work with Democrats, as in 2009 when he joined former Sen. Russ Feingold, D-Wis., and Sen. John McCain, R-Ariz., in proposing legislation to give the president line-item veto power to remove wasteful earmarks from legislation.
Still, Ryan has not been shy about protecting provincial interests. An avid bow hunter, Ryan in the past has tried to assist the American bow hunting industry by including provisions in tax bills requiring foreign makers to pay a tariff equal to the tax paid by domestic makers of the equipment.
Ryan was born and raised in Janesville, a southern Wisconsin town near the Illinois border. After graduating from Ohio's Miami University, he worked for a string of Republicans in Washington, including former Sen. Bob Kasten of Wisconsin, former Cabinet secretaries Jack Kemp and William Bennett and former Rep. and Sen. Sam Brownback of Kansas.
He was the youngest member of the freshman class when he was elected to Congress in 1998 at the age of 28, and is now serving in his seventh term. Former President George W. Bush asked Ryan to be his White House budget director in his second term, but Ryan declined.