HOW TERRIBLY prime the time of Marion Barry can suddenly be when it comes to TV debates. Just like that, the mayor who has been everywhere claims to be too absorbed by the press of business to find time for a TV debate, never mind the viewers at home, who do have a certain democratic interest in seeing him and his opponents join in a healthy back-and-forth on the issues. Surely Mr. Barry doesn't think anybody in the home audience is the least bit fooled by this most ancient of political TV tricks. It's the lowliest political profile.

If a mayor is really too booked to drop by a studio for an hour, his priorities -- not the station's -- need retuning. And if, as he says, there is a ward reception and a dinner salute he's supposed to attend on the evening of Channel 4's planned debate, wouldn't his supporters understand? If not, they can't be such strong supporters after all.

Of course, there is no guaranteed insight for viewers in televised debates. Still, how better to share with the maximum number of people -- including many around town who do not or cannot physically attend any forums -- the views, reactions and interplay of ideas that good candidates should be prepared to present in their quests for public office? If an incumbent believes in his record, won't it hold up on camera, live, against all challengers?

Mr. Barry is scheduled to appear on one taped forum scheduled by Channel 4 at 7 p.m. Saturday. But this station, as well as Channel 7, has offered live, prime time, too. There is precious little of that left before the primary -- and the mayor should seize it.