THE HOUSE Democrats are threatening to renege on a leading enforcement provision in the October budget agreement with the president. The president has threatened in turn to veto any spending bill in which they try to do so, even if he has no objection to the spending itself. The anticipatory bluster on both sides is aimed at solving a problem that hasn't occurred. Until one does, the combatants should keep the procedural peace.

The dispute involves the tricky business of cost and revenue estimating on which, for better or worse, the legislative process has come increasingly to depend. The anonymous estimators constitute almost a separate branch of government. They have enormous influence when legislation has to be fiscally neutral, a standard that was imposed on tax reform in 1986 and welfare reform and catastrophic health insurance thereafter. Estimates -- of the likely effect on revenues of a capital gains tax cut, for example -- have played a prominent part in the tax and budget debates of the Bush administration with Congress as well.

Because the estimates are both central and manipulable, in that they necessarily rest on shaky assumptions, it becomes important which branch does the estimating. The original Gramm-Rudman legislation encountered this problem and tried to solve it by a compromise, giving the General Accounting Office the tie-breaking right to determine when and how large an across-the-board spending cut was called for. The courts struck that down for breaching the separation of powers, in that GAO, a congressional agency, was triggering an executive act. A qualified estimating power was finally given to the Office of Management and Budget.

The October agreement did much the same. OMB was given the power to see that appropriations bills do not exceed negotiated spending caps, and that tax and benefit bills affecting the parts of government not subject to the appropriations process are self-financing. If it seems to OMB instead that a tax-and-benefit bill will increase the deficit, the president is empowered to cut other benefit spending to make up the cost.

That's the authority the Democrats want to take back. The Joint Committee on Taxation and Congressional Budget Office would estimate the budgetary consequences of every tax-and-benefit bill. Every such bill would then include a paragraph saying that, for the purpose of enforcing the budget agreement, the president should accept those estimates. The Democrats say they need to know in advance what side effects a bill may have, so that if an increase in veterans' benefits is going to trigger a cut in farm supports, for instance, they can legislate both and not have the latter come without forethought and by meat-ax. They also say OMB can't be trusted not to skew its estimates for political purposes. The administration makes the opposite argument -- that Congress can't be trusted to be the judge of its own work.

But surely it's possible to reach an understanding whereby OMB gives its estimates far enough in advance of the final vote on a bill to give Congress time to adjust. If OMB does indeed hype a provision's cost for political purposes, that will be the time for Congress to take back the estimating power. This is a pretty well-balanced agreement. It ought to be given a chance to work before it's changed.