THE DISTRICT'S proposal to find a private developer to build a downtown campus for the University of the District of Columbia begs one question: does UDC need a downtown campus? When Sen. Patrick J. Leahy first raised that question several years ago, we thought about it and concluded that there was no doubt of the need. But we've continued to think about it, and we have to confess to you that the case for the downtown campus doesn't look as strong today as it did in 1978. What accounts for that change of view? Inflation, the financial squeeze on the city, and the prospect that the university's enrollments will not greatly expand in the 1980s. To justify another campus will require a better argument than the university has yet made for it.

On the crucial point, enrollment at the school is not projected to rise by more than 4,000 students in the next five years from the current level of 14,115. Sen. Leahy said he would prefer to see the school's new Van Ness campus expanded instead of building an additional campus. The response from city and school officials has been that the Van Ness campus cannot accommodate any more buildings; the vacant land next to the campus is the property of the State Department. Also, it is argued, the Van Ness campus is not in easy reach of working people who have to leave jobs downtown and travel up Connecticut Avenue to take night courses. The cost of the buildings now being leased by UDC is another consideration put forth by proponents of the downtown campus. To meet the objection that building a second campus would be too expensive, the city has come up with a plan that avoids laying out cash. A private developer would lease half of the city-owned land at Mount Vernon Square now reserved for the UDC campus in exchange for building a new $40 million classroom complex on the rest of it. When the lease expired, the city would give to the university the land, the college building and whatever hotel or office building the developer had built. The continuing profits from the private development would become an endowment.

This plan, for all its elegance, merely conceals the cost. Instead of providing money, the city would pay with valuable land. That price is not small, and a project on this scale requires the most careful examination. The discussion keeps coming back to the central issue of future enrollments and the students' requirements. Until a second campus can be fully justified in those terms, it really doesn't matter how clever a scheme the city develops to finance its construction.