WASHINGTON - Now what?

With the stimulus plan all but done, President Obama faces a host of opportunities - and as many hurdles - in choosing his next big push.

Overhauling health care is a logical choice, but there is no health secretary or White House point person now. The president has promised a summit on entitlement costs but has done little spadework. Advocates want major changes in energy and immigration policy, yet deep divisions remain.

Moreover, Obama just spent considerable resources persuading a wary Congress and public to accept multibillion-dollar plans to spur the economy and rescue the financial sector. With those programs just beginning, he says the nation cannot wait to tackle even more expensive problems: fixing the long-term funding mechanisms for Medicare, Medicaid and Social Security.

Dealing with the immediate economic crisis means massive spending, huge deficits, and widespread tax cuts. The longer-term cures for entitlements and budgets call for spending cuts, smaller deficits, and likely tax increases.

"How do you mesh those two without making people get dizzy?" said Henry Aaron, an economist at the Brookings Institution who tracks government actions.

Some in the administration and Congress ask a more basic question: How many big, expensive, and ambitious initiatives can the country swallow at once, especially when partisanship in the House and Senate appears unabated? As Aaron put it, "This is not the environment that seems conducive to grand bargains."

But Obama says he wants to do big things and avoid playing "small ball," even if there is no rest between innings.

For instance, five days before his inauguration he told Washington Post editors that he would convene a "fiscal responsibility summit" in February to tackle questions of entitlement overhaul and long-term budget deficits. "We have to signal seriousness in this," he said, by making sure some of the hard decisions are made under my watch, not someone else's."

With February half gone, Obama has not set a date for the event, although senior adviser David Axelrod said an announcement would be coming soon. Meanwhile, the leaders of groups heavily involved with Medicare and Social Security say they have heard little or nothing about the summit, so they don't know what to expect. Some are urging Obama to be bold and ambitious, even as Republicans pound him for pushing the $789 billion economic stimulus through Congress.

The Peter G. Peterson Foundation is running ads calling for a bipartisan commission to make far-reaching recommendations for Social Security, Medicare, spending, and taxes that would be subject to limited amendments in Congress.

"The normal legislative process is clearly dysfunctional" in coping with such big issues, David M. Walker, the foundation's president and former comptroller general of the United States, said in an interview. The public may be reeling from the size of the stimulus and bailout packages, he said, but the economic crisis is "a teachable moment" showing that budgets, deficits, entitlements, and taxes are interwoven.

"To do a grand bargain" that forces all sides to sacrifice something for the greater good, Walker said, a government "must work on multiple things at once."

Axelrod said in an interview yesterday that the administration wanted to move on multiple fronts and "keep the momentum going." Besides putting the stimulus plan in place, he said, the White House will focus on housing, education, energy, and health care.

"If you view these things in isolation, I think they can be daunting," Axelrod said. "They become fodder for the kind of political small ball that sometimes consumes Washington."

He acknowledged that plans for health care were interrupted by Tom Daschle's failed bid to become the White House's health chief as well as Health and Human Services secretary, and that matters aren't helped by Sen. Edward M. Kennedy's absences from Congress because of illness. Kennedy (D., Mass.) heads the Senate committee that deals with health-care matters.

This week in Florida, Obama said he soon would announce "what our overall housing strategy's going to be." He will outline more plans in a speech to Congress on Feb. 24.