IS SUNLIGHT IN THE CAPITOL worth saving? Rep. Robert K. Dornan, a freshman Republican from California, raised that question last week during the House fight over the latest plan for extending the West Front. "I would beg this House," Rep. Dornan said, "not to close off forever the sunshine that streams in the corridor windows down the spine of this beautiful Capitol."

He was talking about the short stretches of corridor just outside the House and Senate chambers, where West Front windows bring afternoon sun into the public halls and also provide a stunning view of monumental Washington.The charm of a few windows may seem like a minor point. What Mr. Dornan meant to evoke, however, was something more: the sense of tradition and continuity that would be lost if the old facade were shut off from the world behind a new marble addition full of offices.

To their credit, many of Dr. Dornan's colleagues share his regard for preservation of the historic Capitol wall. In fact, the House leadership had to scramble to get the $55-million extension plan approved by a thin margin, 212 to 204. And the closeness of that vote encouraged Walter Huddleston (D-Ky.), chairman of the Senate appropriations subcommittee, to announce a few days later that his panel opposes the project and prefers repair and restoration of the original sandstone facade.

If the full Senate supports restoration as in the past, the latest raid on the West Front will have been foiled. Congress should then get on with the repairs, which are so overdue. Meanwhile, the House could assuage its hunger for more Capitol offices and meeting rooms by moving some support facilities elsewhere on the Hill. As several representatives suggested last week, one obvious candidate for relocation is the Architect of the Capitol. His staff now occupies some 50 rooms totaling 22,000 square feet of prime Capitol space - mostly on (where else?) the West Front. Perhaps he would think better about his plans for defacing one whole facade of the Capitol if, instead of being on the inside looking out, he were on the outside looking in.