That Social Security is in serious trouble is hardly news. For the large tax increases enacted by the 95th Congress in 1977, Social Security remains what former Sen. Harrison Schmidt called "a time bomb ticking." And the fuse is dangerously short: according to current projections, the Old Age and Survivors Trust Fund will run out of money by the middle of next year.

Changes in Social Security will be enacted by the 98th Congress. There is simply no more time for delay. Exactly what will be enacted, however, is an open question. A host of controversial proposals have been put forward, including increasing taxes, raising the retirement age, cutting benefits, enrolling federal employees and funding the system out of general revenues.

No matter what decisions are made, Congress will be accused of pursuing narrow political interests. While such charges are unavoidable, there is one way Congress could gain public confidence. Congress should join the system.

As it is, many members and congressional employees have paid Social Security taxes in the past, and some will do so in the future. These individuals will, of course, collect benefits upon retirement. Yet exempting current congressional employees from Social Security taxes, permits Congress to have its cake and eat it too. The existing congressional pension plan is, by any measure, very generous. While many employees in the private sector contribute to a pension plan and pay Social Security do so without a direct stake in its future. For many members and staff, this amounts to simple tax avoidance.

It is no surprise that Congress and its staff doesn't pay Social Security taxes. Congress regularly exempts itself from laws it finds burdensone. The legislative branch isn't covered, for example, by the equal-employment laws. Congress has also exempted itself from the Occupationl Safety and Health Act. Congress has also excused itself from the provisions of the Clean Air Act. A commentary, perhaps on the lasting importance of smoke- filled rooms.

Social Security is the most important domestic program run by the federal government. The custodians of the system can no longer be excused from participating in it. For at least four reasons, Congress and its employees should begin to pay Social Security taxes immediately. The first reason is simple integrity. Signing up for Social Security would be a symbolic act of real significance.

The second is financial. There are more than 30,000 employees in the legislative branch. If these employees contributed only $1,000 a year, the Social Security system would be $30 million richer each year. While this would hardly solve the system's fiscal problems, it is a step in the right direction.

Third, by joining Social Security, Congress has the opportunity to demonstrate a real commitment to the financial health of the system. Nothing will illustrate congressional support for Social Security quite as clearly as paying taxes to support it. Lofty language in not sufficient; Congress should put its money on the line. This also provides some measure of political plausibility: if Congress raises taxes, it raises its own taxes; if it cuts benefits, it cuts its own benefits.

Finally, Congress should participate to regain public confidence. It's no secret that politicians are unpopular. In opinion polls, members of Congress rank only slightly ahead of used-car dealers in trustworthiness. Little wonder. Over the last decade, the public has been treated to a continuing spectacle of life imitating art; there are more sex scandals and criminal indictments on Capitol Hill than in TV soap operas. Highly publicized attempts to raise congressional pay and create generous tax breaks diminish Congress' standing further. Similarly, enacting major laws and regularly excusing Congress from coverage only reinforces public cynicism about the political process.

Obviously, one action will not reverse the decades of preferential treatment Congress has accorded itself, nor will it lift the veil of cynicism and suspicion that clouds our political process. It would, however, be a very visible step in the right direction.