IT WAS inevitable that the mood of budget-cutting sweeping Washington these days would find expression on Capitol Hill in an effort to amend the Constitution. But that is no justification of the warm reception the proposed balanced-budget amendment got from key members of the Senate Judiciary Committee on Wednesday. The amendment is questionable economics, at best, and terrible law.

Under its terms, Congress would be required to adopt a budget each year in which expenditures do not exceed revenues, except in those years when war has been declared or when three-fifths of each house vote not to. As variants of this kind of proposal go, this one is a moderate version. But that is about all that can be said for it.

The case for this amendment rests on the theory that a balanced budget is almost always the key to national economic health and on the belief that members of Congress are unable to restrain their spending urges sufficiently to provide that kind of budget voluntarily. The former may or may not be true; even if it is, the idea of writing economic theory into the Constitution conflicts with that document's basic principles and its history. As for the idea that restraints of this kind are required, how does that jibe with the view that the voters demanded fiscal restraint in the recent election and will bring to defeat, the next time around, anyone incautious enough to be a big spender.

On other grounds, the case for this amendment is equally weak. The federal budget rests on estimates, prepared almost two years before the close of each fiscal year. In a changing economy, there is no way those estimates can be accurate. (The current year's budget, remember, was in balance briefly last spring based on the estimates made then; it is now some $50 billion out of balance.) There is no mechanism through which a constitutional amendment can force a president or Congress to be more accurate or to stop adjusting the estimates -- as the administration has just done -- to make them come out right.

In other words, the proposed amendment is a fake. When the political will exists to balance the budget, it will be balanced. When that will does not exist, there are innumerable ways to make an unbalanced budget appear balanced. e

Because constitutional amendments are not self-enforcing instruments, the burden of any attempt to enforce this one would presumably wind up in the federal courts. Thus, this particular amendment is either hortatory in nature (and does not belong in the Constitution) or is an effort to put even more power in the hands of federal judges.

Instead of embracing this idea, members of Congress should be telling the legislatures in their home states to head off the effort to call a constitutional convention to propose such an amendment. Neither a convention to propose such an amendment. Neither a convention nor an amendment. Neither a convention nor an amendment is likely to do any good. Both could do great harm.