FOR TWO YEARS NOW, President Clinton has used the shaky financial condition of Social Security to thwart the Republicans on the budget. They want to use the plump surpluses projected to finance a large tax cut. Fine, he says, but surely not at Social Security's expense. To ensure that they're not diverting to a tax cut money that will be needed to shore up the old-age and disability insurance program, they should "save Social Security first" has been his slogan. Partly because the merits are on his side -- the government can't afford a large tax cut given the long-term Social Security and other costs it faces -- Clinton has prevailed.

Now the Republicans have begun to play their version of the game. To guard against the charge that they are raiding Social Security to pay for tax reduction, they propose to set aside in a parliamentary "lockbox" all the prospective surplus attributable to Social Security -- its current excess of revenue over costs. In theory, only non-Social Security funds then could be used for most other purposes, including a tax cut. The position sounds about as virtuous as it is possible to get on the subject, and the House last month passed a lockbox bill by a vote of 416 to 12, with Democrats mocking the measure but in the end joining Republicans in support lest they be the ones accused of less than total zeal on Social Security's behalf. The Senate Republican leadership may try to bring up the same or a similar bill this week.

But this is phony legislation, and it would do no good, and it is possible to imagine circumstances in which it would do harm. Its purpose is to protect the politicians, not the program, and most of it is merely a showy restatement of the status quo. But it also implicitly would ease the current definition of fiscal discipline and in doing that could end up weakening precisely the values it pretends to strengthen.

The first point to be made is that the lockbox doesn't have a lock. The bill does no more than create a point of order against measures that would add to or acquiesce in deficits in the non-Social Security part of the budget; those are the deficits that over the years Social Security funds have been used to cover. But the points of order could be waived by majority votes in the House and 60 votes in the Senate. Those are the same margins needed to pass such legislation now; there would simply be another hoop to go through.

The legislation would do nothing to solve the Social Security's financial problem either. The long-term mismatch between prospective revenues and costs would continue to exist. Nor would the bill make any operational change in the shorter run. The Treasury would continue to "borrow" the annual Social Security surpluses, depositing IOUs in the trust fund in return. The only issue is what use would then be made of the money. The lockbox bill says that, without a waiver, the funds could be used only for Social Security or Medicare "reform," neither of which is defined, or to pay down debt. But the bill's own sponsors just finished voting to use such funds to pay for a so-called emergency appropriations bill to which billions of dollars in non-emergency items had been added for the ride, and every House member of both parties who voted for the lockbox bill understands that the same funds are going to be heavily tapped later in the year to help pay for the regular appropriations bills as well.

The lockbox is thus a sham. The extra hoop could, however, have the unintended effect of complicating and slowing down future responses to recessions and real emergencies. At the same time, so long as a non-Social Security surplus existed, were the lockbox rules to become the norm they would make it easier than now to enact a tax cut or vote for a spending increase. Under current rules, the cost of such actions is supposed to be offset whether there is a temporary surplus or not. The lockbox bill turns a surplus into a license. In the name of protecting Social Security, it would help to legitimize the tax cut the president rightly has resisted and the Republicans seek to enact -- and that is no accident. This is legislation whose main intent is to deceive, and whose main effects could well be harmful. It ought not become law, but the House vote suggests it very likely will. If so, there should be no illusions about what has been achieved.