Former Arkansas Gov. Mike Huckabee, who won the 2008 GOP Iowa caucus, applauded Ryan, but noted the proposal has little chance of enactment so long as Democrats control the White House and Senate.
But Ryan's plan has gained so much attention and praise in Republican circles that the contenders won't be able to ignore it for long, if they want to seize control of the debate on their terms.
Candidates who appear tepid about Ryan's cost-cutting might lose favor in primaries dominated by debt-hating conservatives. But heartily embracing the proposals could haunt the eventual nominee if President Barack Obama can portray his challenger as recklessly willing to undercut health care for the poor and elderly.
Dan Schnur, a former aide to Republican presidents and governors, said the contenders are smart to keep their heads down.
"They can't compete for headlines with either the governors or the Republicans in Congress," said Schnur, who heads the Jesse M. Unruh Institute of Politics at the University of Southern California. "So they might as well keep their distance until the dust settles. But at a certain point, those candidates are going to have to engage."
History suggests they be wary of seeking significant changes to Medicare, Social Security or subsidy programs without at least some Democratic support.
One-party drives typically have failed. In 1981 and 1985, President Ronald Reagan and GOP lawmakers unsuccessfully tried to trim Social Security benefits. Gingrich's failed effort to rein in Medicare in 1995 led to politically damaging government shutdowns. President George W. Bush got nowhere with his 2005 bid to partially privatize Social Security, which Democrats denounced.
Happier results came from bipartisan agreements to raise Social Security's eligibility age and payroll taxes in 1983, and to curb welfare benefits in 1996 under President Bill Clinton.
Ryan calls his proposal a cause, not a budget. Such remarks may rally conservatives who say it's time for painful medicine to cure the nation's growing debt habits. GOP presidential candidates will need these voters in the Iowa caucus, New Hampshire primary and beyond.
But by the fall of 2012, Obama may try to convince independent voters that his GOP opponent has embraced a partisan cause rather than a fair, even-handed spending agenda for America.
His allies are laying the groundwork. Ryan's budget "represents the victory of the tea party mentality over mainstream conservatism within the Republican Party," said Bill Galston, an aide in the Clinton White House.
If that message resonates with a wide audience, Ryan's ambitious plan may leave a dubious legacy.
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