WILL WASHINGTON continue to capitalize on what has been a relatively healthy urban economy and become an even more attractive place to live and work? In the fours years ahead, will this city's mayor see today's seeds of commercial activity around town grow into flourishing job-creating projects? While no one running for mayor promises you a metropolitan rose garden, there is optimism in the message of each candidate. No contender foresees the withering of the capital city. But all of them recognize the challenge of addressing the likely slowdown of at least the rate of growth of the federal presence here.

Mr. Barry, Mrs. Harris, Mrs. Jarvis and Mr. Ray are well aware of the unemployment that scars the lives and hopes of too many city residents in general and of a staggering number of young blacks in particular. Part of the response, as each candidate notes, must be generated in the city's schools. Mr. Barry's experience with the school system is strongest of the four leading candidates, and he has cooperated with School Superintendent Floretta McKenzie in her efforts to draw private industry into the training programs offered in the classroom.

Complementing these efforts is a summer youth jobs program that has overcome most of its earlier organizational difficulties to become one of the most effective programs of its kind. Many of its participants are kept on by their employers for part-time work year-round.

The number of private in-city job opportunities, however, still has to grow. The business leaders who have worked with the city government on the new downtown plan, and on the comprehensive plan soon to be issued, will look for still more assurances that economic growth will not be frustrated by unnecessary red tape or unfair tax burdens. On this point, too, all four candidates pledge a climate appealing to business: development corporations and new incentives aimed at attracting certain businesses to various parts of the city.

If the fruits of the mayor's labors in this sector so far seem to fall short in the eyes of his challengers, current projects do point to constructive changes in the face of the city: at 8th and O streets NW, the first new supermarket in the city in 10 years, a Giant; in the new Hechinger Mall, a Safeway; under construction, the Grand Farmers Market; and downtown, the Convention Center, planned not only as a major generator of jobs but also as a magnet for development around it.

For the future, each candidate can tick off an almost identical list of familiar proposals for generating development -- combining government help with financing from private banks, union pension funds and tax incentives. But just as bureaucratic disorganization can frustrate the pace and coordination of economic growth in a city, so can the sort of criticism that calls for more planning groups, commissions, re-studies and total overhauls of things that are already in the works. That can be a weakness in the agenda of a challenger, not a contribution to renewed urban health.