SHOULD THERE be a National Theatre in the 1300 block of E Street NW? That is what the Pennsylvania Avenue Development Corporation must decide as it chooses a plan for the redevelopment of the block. In carrying out its congressional mandate to revitalize the area between the White House and the Capitol, the PADC concluded that the block was just right for offices, hotels, stores, restaurants and other enterprises that could spark some life downtown. The corporation is now reviewing three proposals from developers, one will be chosen in a few weeks. Each proposal offers an interesting architectural design, a mixture of office, hotel and commercial space - and the possibility that some new night life will be added to the area. But while one plan calls for a new theater to be built on the block and another leaves the theater as it is, third requires that the theater be removed from the site altogether.

The scheme that would send the theater packing is the work of the well-known architect and developer John Portman, who has been retained by the National Press Club. As the primary owner of the National Press Building, also located on the block, the Press Club has more than a passing interest in the future of the site. Members of the club were at first interested in having the theater as a neighbor, they have been strong supporters of it in the past. But after lengthy discussions with National's board of directors, the Press Club/Portman group concluded that a theater would be too expensive. Instead, the group suggested that the National move its productions down the street to the Warner Theatre and that a new theater be built somewhere else in the area.

It should come as no surprise that the National's board members don't favor the Press Club/Portman plan. For one thing, they don't think that the Warner Theatre - now used mostly for rock concerts - would be able to handle their productions, even if it were to be substantially renovated. The board members also know that, without adequate arrangements for the interim, they will be out of business for at least three years while they wait for a site to be found and a theater to be built. National's board believes the other two proposals under consideration offer it a chance to stay on the block. The bid submitted by local developer John Ackridge, for example, calls for a new theater to be built on the block even before the present one is torn down; productions could continue without interruption. Another offer, made jointly by the Quadrangle and Marriott corporations, would leave the National just where it is - with no changes whatever.

Despite ravages of several fires and a number of darkened months, the National Threatre has been located in the 1300 block of E Street for more than 140 years. It is considered the oldest continuously run theater in the country and has provided such theatrical events as the original version of "Ben Hur" (with horses and camels on stage), the first chance for Alfred Lunt to meet Lynne Fontanne - and hundreds of musical and dramatic productions, including "Showboat," "The Miracle Worker," "Hair" and "Hello, Dolly." The National Theatre offers the kind of night life that the PADC has said should be on that block. In one form or another, it ought to stay.