THE FIRST STEP toward solving any political problem is to get people to admit the problem exists. The National Commission on Social Security Reform, meeting this week in Washington, has already made a huge contribution by getting its members of different political persuasions to agree that Social Security's problems are real, urgent and -- within reason -- measurable.

As the commission sees it, Social Security faces three perils: a shortfall of revenues over the remainder of this decade; a longer-run deficit growing acute after the year 2020; and a continuing vulnerability to downturns in the economic cycle. There is also significant -- but not unanimous -- agreement among members on what a solution should look like: current beneficiaries should not suffer outright reductions in benefits; those nearing retirement should not face abrupt changes in potential benefits; the burden of putting Social Security on a sound basis should not fall entirely upon the working population.

The size of the long-term deficit is, of course, the most speculative element, depending as it does on assumptions about birthrates, longevity, immigration and economic conditions well into the next century. But enough is known about future population trends to know that trouble is coming. That means that in evaluating short-run measures, preference should be given to those that promise substantial savings in the long term as well.

For the short run, the commission agreed that if slow growth continues through the rest of the decade, the Social Security trust funds may need a boost of more than $150 billion during that period. A deficit that big can't be closed without raising payroll taxes. However, other options -- such as covering new federal employees, delaying cost-of-living adjustments and taxing part of Social Security benefits received by the relatively well-to-do --should also be included, both to make the system fairer and to help out with the long-run deficit.

As Commission Chairman Alan Greenspan pointed out, Social Security also needs long-term "fail-safe" mechanisms. These would protect it against the combination of events that are the main source of its current difficulty -- slow economic growth with wages lagging behind inflation. This can be done either by adding other taxes to the trust funds in bad times or by temporarily curtailing improvements in benefits.

Early in the next session, Congress must sift through the commission's proposals and reach a bipartisan consensus about which ones to put into law. That task wasn't made easier by the partisan bickering over Social Security during the election campaigns. House Ways and Means Committee Chairman Dan Rostenkowski, however, got the process of compromise off to a good start this week by sending a letter to all House members. "Keep your powder dry," the chairman urged in reminding his colleagues that, whatever sacrifices may be required, the main concern of the public is that the Social Security system be put on safe ground for the foreseeable future.