This is the essential question for Rep. Paul Ryan: Can this man really manage the hardest sales job in U.S. politics?

Ryan (Wis.) is the lanky, wonky chairman of the House Budget Committee. This week, he is stepping into a role he has been seeking for years: point man for a historic Republican effort to reshape very popular, very expensive programs such as Medicaid and Medicare.

He is detailing those efforts as he announces his budget plan for fiscal 2012. In a news conference Tuesday morning, he was moved almost to shouting, saying he had finally proposed a “fact-based budget.”

“The sooner you act to fix it, the better off everybody is,” he said, laying out the heart of an appeal for Americans to cut their own future benefits.

So far, the sales pitch appears to be classic Ryan. He will make his case with earnestness and a hope that a quiet explanation of budget math can swing the country in a way that previous politicians could not.

“We have a choice of two futures,” Ryan says in a video that explains his spending plan. Appearing in shirtsleeves, he outlines two scenarios: rocketing debt, if the status quo is maintained, or shrinking spending under his “Path to Prosperity” plan.

“It is up to our generation to pick this path,” he says. “The question is: Will we do it or not?”

Ryan’s proposal for next year may be overshadowed this week by the ongoing fight over this year’s budget. That tug of war, in which Republicans and Democrats have been unable to agree on spending cuts, threatens to cause a government shutdown Friday.

But, when the battle clears, Ryan is poised to start an even bigger one.

The current spending fight deals with a few tens of billions of dollars; Ryan’s plan aims to cut more than $6.2 trillion in federal spending over the next decade. It also asks Americans to accept cuts in some of the government’s most beloved programs in the name of keeping the programs solvent for years.

Ryan, 41, seems like an unlikely revolutionary. He has been in Congress since 1999, after being elected at age 28 to represent the district that includes his home town of Janesville, Wis. His district voted for Barack Obama in the 2008 presidential election.

Ryan studied economics in college, and in Congress he has embraced the weedy issues of the federal budget. But as recently as last fall, his broader proposals seemed to have little support within his party. When he pitched a “Roadmap for America’s Future,” with many of the ideas contained in his budget plan, just 13 of 178 Republicans initially signed on as co-sponsors.

Now, however, as a wave of freshmen obsessed with controlling spending has shifted the GOP’s ambitions, Ryan’s ideas have been embraced.

“Our vision is reflected in this fact-based budget for America’s future,” House Majority Leader Eric Cantor (R-Va.) said in a statement Tuesday.

Ryan’s plan includes changing the Medicaid program, which provides health care to the poor, so that states receive federal money in block grants. States then could determine how to draw their programs. Republicans see an opportunity for greater efficiency. Some Democrats view it as a chance to cut the aid the programs provide.

The vision also includes a change in the Medicare program, in which the federal government acts as a health insurer for seniors. In coming years — Ryan’s plan does not apply to people who are already 55 — he would shift the program so that seniors would choose a private health plan. The federal government would then provide “premium support” to help them pay for coverage.

In the past, other more famous and more charismatic Republicans have tried to overhaul such large programs, only to fail. Then-House Speaker Newt Gingrich (Ga.) tried to reform Medicare in the 1990s, and that dispute was partly to blame for a politically disastrous government shutdown. President George W. Bush sought unsuccessfully to overhaul Social Security in 2005.

Now, political observers say, Ryan is starting with even greater disadvantages.

“Nobody knows who Ryan is, outside his home area,” said Allan Lichtman, a professor at American University. “I don’t think he has the clout, the charisma, the political power to do this.”

But if Ryan has any chance of shifting the politics of these “entitlement programs,” then Sarah Binder, a professor at George Washington University, said sticking to his wonky reputation would be a good idea.

“To the extent that he’s able to sort of keep his policy-wonk reputation front and center,” that helps, Binder said. She said Ryan’s best opportunity is to be seen as above party squabbling. His persuasion depends on him instead being viewed as an independent, concerned voice.

Even then, though, she said Ryan’s chances aren’t great.

“Typically, voters like short-term benefits, with the costs put off to the future,” Binder said. Ryan’s vision relies on them agreeing to short-term changes, with benefits further off. “You can’t do that without the president, and you can’t do it without the support of both parties.”