This city is rough on the spouses of its wielders of power, and most of all on the wife of the president of the United States. Whoever she is, she operates by borrowing the earned authority of her husband, and she is constantly reminded that she is something of an interloper. She has no official duties, but she is accountable unofficially to a vast flight of eagle-eyed observers. In these circumstances, it is hard to do much right.

Nancy Reagan, however, has done something extremely right. She has thrown herself into the fight against drug abuse with vigor and intelligence. If she had simply been shopping for a worthy cause, she might have picked a homier, more heartwarming or more photogenic one. Instead, she picked a relatively ungainly and untended one where her particular contribution could be of special value: to display a personal commitment and to use the public's, the media's and even the bureaucracy's inevitable interest in her to draw others to the cause.

The conference that Mrs. Reagan is running yesterday and today is a good illustration of her work. In an unprecedented initiative, she has brought together the wives of the leaders of 17 foreign countries in order to publicize the global nature of drug abuse -- and of caring about drug abuse. This latter element emerged strongly from the conference yesterday. The women attending seemed quite aware of the limitations of what they in their particular role can do. There was evident, however, an awareness of the human dimension of the drug problems in their respective countries, and of the requirement for a stronger community of concern rooted in family values and family ways.

Does it make a difference in the end? How can it not make a difference for the idea to spread that drug abuse compels the alarm and the informed attention of responsible women like these? Their governments, while all friendly to the United States, are not all equally cooperative and like-minded in the often very political matter of drug cooperation. Such difficulties are not to be swept under the rug, but the personal warmth and the shared purpose evident at the conference are important assets. For using the resources of her position to increase them, Mrs. Reagan deserves gratitude.