(FORTUNE Magazine) – All summer long Washington has burned over the issue of a tax cut: How big should it be? Who should get it? How will it affect the economy? The debate is certain to smolder into the fall. But in almost every way, it's a phony fight over a phony issue. The real debate, in this era of surplus, is not about the size of your tax cut. It's about the size of your government.

As happens so often in Washington, the rhetoric here simply isn't tracking the reality. Politicians of both parties are guilty of fuzzing the issue. Stump speeches aside, Republicans have always been just as interested in trimming government as in trimming your tax bill. And while Democrats can swallow a modest tax cut that lets them crow about putting a few more dollars in your wallet, their hearts' desire is to spend, spend, spend on education, health care, welfare--you name it.

Although Ronald Reagan never said as much, one of the principal goals of his 1981 tax cut was to thwart Democratic spending impulses, making it indecent to propose new government programs while the deficit war was on. His strategy worked. The federal budget was 22.2% of GDP at the beginning of the Reagan era. Today, it's 19.7%--and will be even lower by the time the fiscal year ends next month.

The tug of war over the budget surplus highlights one of Washington's counterintuitive little secrets: The surplus terrifies conservatives. They know that liberals abhor a spending vacuum, and that Democrats will rush to fill it if they can with all manner of social programs. "Ultimately this debate is about putting a brake on the ability of government to spend," says Stuart Butler, the vice president for domestic research at the Heritage Foundation, the conservative think tank.

The great irony here is that while Washington talks a torrent about taxes, the country isn't talking about them at all--not debating on the beach how to distribute the booty, not dreaming at the lake of how to spend the windfall. Indeed, in Washington's rush to cut taxes, an important poll finding has been brushed aside: Most Americans consider a tax cut a small priority. And small is the right word. This tax cut isn't big enough to buy an extra pizza every two weeks. "This tax break is nothing," says Representative Edward J. Markey, a Massachusetts Democrat from a classic middle-class district. "The Republicans simply can't create a tax break that in any way compares with what the stock market is providing to these families."

So what's the fuss all about? Certainly not about you or me. It's about high-minded politicians of both parties who take credit for debating one thing--the size of your tax cut--while doing something else entirely: arguing over the size of your government.

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