FRANKLY, IT HAD NOT previously occured to us to wonder if Walter Fauntroy, the District's congressional delegate, is a CIA agent. He is ordinarily an open-mannered and open-minded fellow who occupies himself diligently and, we think, on the whole effectively in his duties on Capitol Hill. He is not given to slinking around corners, putting on gloves before opening doors or wearing a trench coat - the usual tipoffs of a secret agent. We find it extremely difficult to believe that Mr. Fauntroy has a secret master as well as a public one.

We have recently detected, however, a startling and startlingly suggestive pattern. Mr. Fauntroy serves on the House Assassinations Committee; he is chairman of its subcommittee investigating the murder of Martin Luther King. The inquiry and subinquiry have had great difficulty getting off the ground. In seven months of existence there has been produced a great deal of confusion and controversy but, so far as we and most others can see, neither helpful new information nor the promise of same. Why is this so? What is the reason for the Assassinations Committee's ineptitude and failure?

Perhaps now you see why we feel obliged to raise the grave question of whether Mr. Fauntroy is a CIA agent assigned to shift the focus of the inquiry from substance to sideshow issues in order to protect the agency. Think of it: Mr. Fauntroy has a perfect cover. Who would suspect a legislator of being a CIA agent? He has an excellent reputation for integrity and honesty - perfect for denials. He is ideally placed, right inside the committee, to sow uncertainty and disinformation and to undermine its work. True, it is a bizaree possibility, but has not recent history taught us to look first at the bizarre for the hidden truth? Indeed, given this strange pattern, would it not be wise for the committee to investigate the CIA's possible penetration of the committee's own ranks?

Actually, we think it's a lousy idea. But it's no worse than Mr. Fauntroy's own idea that the committee should investigate the possible CIA ties of some of the reporters assigned to cover it. What leads Mr. Fauntroy to make this suggestion? If you can believe it, certain ink-stained wretches have had the temerity to write stories indicating that the committee isn't doing much of a job: circumstantial evidence, in the Fauntroy view, that they're working for the CIA. In fact, Mr. Fauntroy imaginative charge is circumstantial evidence of quite something else: The reporters are on the right track.