It's a slow day. The nightly news show shuffles through its time slot, and on to the closing hymn: "That's the way it is, Thursday, June 12, 1980, the 222nd day of captivity for the hostages in Iran. This is Walter Cronkite, CBS News. Good night."

The line is delivered in the well-known, well-punctuated, well-modulated, properly authoritative manner -- rather like a benediction. But, after 222 days, this sentence has become the most powerful subliminal editorial in America.

At first, when the feelings of the country ran as red as the letters on ABC's nightly show "America Held Hostage," Cronkite's words on CBS sounded only like a dramatic epitaph to the news.

But we have been through seven months of imminent breakthroughs and ultimate disappointments, botched military missions and fruitless civilian missions. This foreign affair has become also a domestic affair: the situation in Iran has become a situation in the presidential campaign.

Now, the nightly Cronkite count, even more than the small boxscore numbers on the front pages of dozens of newspapers, has become a flag at half-mast, a daily probe of a wound, a political statement.

The closing hymn passes through our minds quickly like a flashcard -- do something! do something! -- reminding us of what we chorus night after night counting the 20th day, the 145th day, the 222nd day of captivity for the American hostages in Iran.

This is not the first time the Iranian story has become a media story. During all those days and nights when we watched the embassy mobs demonstrating again for the camera, the role of the media became a source of concern reported by its reporters.

The media event, the media show, was hardly an Iranian invention. For a long time, journalists had gnawed at the question of whether they were reporting an event or contributing to it. If you cover the event created especially for you, are you being manipulated? If you don't, are you neglecting it?

But in Iran it was so exaggerated that many reporters worried out loud that their own presence produced scenes of "militant students." They didn't know whether they were "manipulating the news" or being manipulated by the newsmakers.

At home, too, the media -- print and television -- were called on to judge the effect of the coverage, as well as the situation, on the Rose Garden campaign.

Most reporters, on and off the air, would rather believe they are covering a story than creating it. So in many ways it has been an uncomfortable time.

Those who deliver the nightly news count also would prefer to think of it as just a fact, a number, with no more impact than the date. Sanford Socolow, executive producer of the CBS Evening News, Says, "I'd like not to think what the effect has been." In fact, he says he hasn't been thinking about it at all.

"The subject [of the evening sign-off] has been mentioned but only cursorily," he said. "This conversation is as deep and as long a one as I've had."

Even at ABC, where they changed the late-night news show's name to "Nightline" when the situation in Iran "abated," Richard Wald said that perhaps the Cronkite line simply "fades into the background like wallpaper."

They were both, I think, expressing a very genuine reluctance of television people to accept the reality of their own power. And perhaps its traps.

"We have to have a reason to stop doing it now," said Socolow. "I don't think Walter and I could get together and say, 'Let's stop it, we're bored with it.' It offends my sense of neatness not to have a reason."

If that is true, then CBS is in, essentially, the Vietnam syndrome. They got into it without thinking about the long-range effects and now are unable to get out of it.

I know the difficulties of this decision. Taking the line off the air can become as much of a statement as leaving it on -- particularly when the president is so eager to convince us that the situation is "manageable." No one wants to feel that we are deserting the hostages and their families, or forgetting. We want the numbers game to end now with their release.

Socolow called the Daily Tally "an item of news, one of several items relative to Iran." But it won't do to pretend that it is just a fact.

Cronkite's show keeps the story not just prominent but dominant, a subtle and powerful daily reminder of our impotence or incompetence, helping no one, not even the hostages. Two-hundreds-twenty-two days of the same editorial is quite enough.