Viewing him as a rising star in the party, Republicans in Congress often talk up Rep. Paul Ryan as a potential governor, senator or House leader. The lanky, youthful-looking congressman from Wisconsin has begged off, citing his young children and limited desire to spend all his time raising campaign money.

Instead, Ryan is running a campaign of a different sort, one his party has so far refused to adopt: He is determined to persuade colleagues to get serious about eliminating the national debt, even if it means openly broaching overhauls of Medicare and Social Security.

He speaks in apocalyptic terms, saying the debt is "completely unsustainable" and warning that "it will crash our economy." He urges fellow politicians, and voters, to stop pretending that this problem will go away on its own.

He administers his sermons with evangelical zeal. He will go anywhere and talk to anyone who will listen. When he is not writing op-eds and appearing on television, he can often be found speaking to liberal and conservative audiences alike about his "Roadmap for America's Future," a plan he says would fix the problem.

"Political people always tell their candidates to stay away from controversy," said Ryan, 40. "They say, 'Don't propose anything new or bold because the other side will use it against you.' "

While he does not name the "political people," they no doubt include many Republican colleagues, who, even as they praise Ryan for his doggedness, privately consider the Roadmap a path to electoral disaster. Unlike most politicians of either party, he doesn't speak generically about reducing spending, but he does acknowledge the very real cuts in popular programs that will be required to bring down the debt.

His ideas are provocative, to say the least. They include putting Medicare and Medicaid recipients in private insurance plans that could cost the government less but potentially offer fewer benefits; gradually raising the retirement age to 70; and reducing future Social Security benefits for wealthy retirees.

Of the 178 Republicans in the House, 13 have signed on with Ryan as co-sponsors.

Ryan's proposals have created a bind for GOP leaders, who spent much of last year attacking the Democrats' health-care legislation for its measures to trim Medicare costs. House Minority Leader John A. Boehner (R-Ohio) has alternately praised Ryan and emphasized that his ideas are not those of the party.

Ryan has not helped to make it easy for his leaders. He is a loyal Republican, but he is also perhaps the GOP's leading intellectual in Congress and occasionally seems to forget that he is a politician himself.

At a recent appearance touting the Roadmap at the left-leaning Brookings Institution, someone asked Ryan why more conservatives weren't behind his budget plan. "They're talking to their pollsters," Ryan answered, "and their pollsters are saying, 'Stay away from this. We're going to win an election.' "

His remarks illustrate the tension among Republicans over their fall agenda. Some strategists say the GOP should focus on attacking the Democrats; others want the party to offer a detailed governing plan.