(FORTUNE Magazine) – There they go again. Talking about new initiatives for health insurance. Making plans to spend billions on schools. Drafting proposals to replace municipal water systems and decrepit bridges. Floating plans to guarantee the tuition of every student at a state university.

Yes, Washington, D.C., is quietly declaring victory over the deficit, and both parties are girding to spend. Even though the budget isn't balanced yet, many of the fiscal restraints the deficit imposed for two decades are about to pop off like so many champagne corks. Happy days are here again. Maybe.

On the surface, there's reason to celebrate. The robust economy is drawing billions of unexpected tax dollars into the Treasury, and the new revenues are like a fresh coat of paint on Washington: changing the look of the place and, just as important, changing the outlook. As it seems increasingly likely that the deficit will disappear before the century does, the entire mindset of the capital is changing. The Business Roundtable is exploring the politics and economics of a budget surplus. Goodbye, Bleak House; hello, Great Expectations.

But while the Senate Dining Room is full of talk of a surplus (not to mention surplus talk), the economic war in Washington is not over yet and probably won't be soon. A zero deficit doesn't mean Medicare is in solid shape. It doesn't mean recessions have been repealed. And there's a big difference between a temporary surplus, which is possible, and a long-term surplus, which is unlikely. "People think you hit zero and you're home free," says Robert Reischauer, former director of the Congressional Budget Office. "The sky opens up, and the message booms forth: You have behaved in a virtuous manner, and all your problems are gone. Not true." Nor should the deficit's demise, even for a short time, be interpreted as a ringing endorsement of Washington's politics. It's the economy, stupid, and not the stupid politicians, that brought us to the point where we can contemplate a deficit of only about $45 billion for the fiscal year ending September 30 and a surplus sometime shortly thereafter.

Even so, the debate over what to do with a surplus that hasn't occurred and may not last has begun in earnest. "This is a fight we haven't had before," says Republican Senator Sam Brownback of Kansas. The irony is that the politics of a surplus are as contentious as the politics of a deficit. There are the spenders who talk about pent-up demand for government initiatives, as well as all those needs that have been ignored in the drive to cut the deficit. There are the folks content to forget the deficit but not the debt, which exceeds $5 trillion. Republican Representative Mark Neumann of Wisconsin already is talking about using the surplus to pay down the debt, and his idea, which would cut debt-service payments, has some generational appeal: Let's free up money to pay for baby-boom retirement benefits. Tax-cutters have their scalpels out too, arguing that the only way to make a surplus permanent is to spur growth through lower taxes. Still, "a one-time surplus that's the result of outside forces shouldn't send people into dreaming about no income taxes," cautions Stanley Collender, managing director of Burson-Marsteller's federal budget consulting group.

Already it's clear that deficit politics and surplus politics have a lot in common. The fight is about money and about priorities. The sentiments are strong, the arguments passionate. Even the first casualty is the same: sobriety.

DAVID SHRIBMAN is Washington bureau chief of the Boston Globe and a Pulitzer Prize-winning political reporter.