About 7 percent comes from the stimulus bill that Mr. Obama signed in February. And only 3 percent comes from Mr. Obama’s agenda on health care, education, energy and other areas.

If the analysis is extended further into the future, well beyond 2012, the Obama agenda accounts for only a slightly higher share of the projected deficits.

How can that be? Some of his proposals, like a plan to put a price on carbon emissions, don’t cost the government any money. Others would be partly offset by proposed tax increases on the affluent and spending cuts. Congressional and White House aides agree that no large new programs, like an expansion of health insurance, are likely to pass unless they are paid for.

Alan Auerbach, an economist at the University of California, Berkeley, and an author of a widely cited study on the dangers of the current deficits, describes the situation like so: “Bush behaved incredibly irresponsibly for eight years. On the one hand, it might seem unfair for people to blame Obama for not fixing it. On the other hand, he’s not fixing it.”

“And,” he added, “not fixing it is, in a sense, making it worse.”

When challenged about the deficit, Mr. Obama and his advisers generally start talking about health care. “There is no way you can put the nation on a sound fiscal course without wringing inefficiencies out of health care,” Peter Orszag, the White House budget director, told me.

Outside economists agree. The Medicare budget really is the linchpin of deficit reduction. But there are two problems with leaving the discussion there.

First, even if a health overhaul does pass, it may not include the tough measures needed to bring down spending. Ultimately, the only way to do so is to take money from doctors, drug makers and insurers, and it isn’t clear whether Mr. Obama and Congress have the stomach for that fight. So far, they have focused on ideas like preventive care that would do little to cut costs.