THE ADMINISTRATION'S "new federalism" plan has entered that embarrassing period when everyone knows that its ailments are terminal but no one wants to pronounce the case hopeless. The White House has assured the public that, despite press reports to the contrary, "constructive discussions" with state and local officials are still in progress on all phases of the plan. The governors say that they will assume the negotiations are still alive until they receive official notice otherwise.

It would be surprising, nonetheless, if the parties were to reach agreement on legislative specifications any time soon, even more surprising if Congress were to find time to consider such legislation in this session, and truly astounding if anything like the administration's proposals were to become law within the next couple of years. This unfavorable prognosis arises partly from the the administration's ill-considered choice of responsibilities to "swap" with states and localities. The trouble is aggravated by the suspicion of many governors and mayors that the proposals are motivated not by a concern for the untidiness of the federal system but rather by a desire to unload major parts of the federal budget onto their shoulders.

These failings might be remedied. What cannot be fixed is the flawed notion that any plan--however finely conceptualized or carefully politicked-- can, in one grand sweep, rearrange the course of any major part of American government. The passion for grand reforms is not, of course, peculiar to this presidency. Every president in recent memory has had majestic designs for tax or welfare reform, urban revitalization, youth employment, overhaul of the federal system or government reorganization. These proposals have followed a drearily predictable path.

A new administration, flushed with victory, hastens to produce a plan making good on campaign promises of major reform. There is a lot of press attention, and Congress promises swift action. Details are worked out, flaws become apparent. The whole thing looks a lot more complicated. Negotiations drag on, everyone loses interest. No one is impolite enough to call the idea dead, but nothing ever happens. A new administration comes along and starts the whole thing over from scratch.

This process wastes a good deal of time, effort and political capital. Worse yet, many good but modest ideas embedded in these comprehensive schemes get lost along the way. The administration has already run that risk with Social Security. The negative reaction to its plans for major overhaul forced the administration to consign consideration of Social Security's imminent difficulties to the twilight zone of a bipartisan commission. Streamlining federal-state relations may now suffer a similar fate.

It is not too late to avoid this pattern in the other major social reform still on the administration's drawing boards, that of health care programs. The fact that those proposals have slipped their due date by several months may be a sign that the original plans for sweeping change have been modified as a result of more careful study of the complexities of the health- care system. When you set out to change the world, you need to know what you're doing.