It was the first time I had ever seen a man snip his nose hairs on prime-time television. But it may not be the last. NBC's new entry into the world, "United States," is nothing if not relentlessly realistic in its description of the dailyness of married life.

But the program that premiered last week is also realistic in another way. Here, for the first time, is a show about the new marriage -- the marriage lived in the shadow of divorce.

Libby and Richard Chapin are not Ozzie and Harriet, or Archie and Edith. In fact, this couple, whose dialogue is as decorator-chic as their living room, reminded me more of Liv Ullman and Erland Josephson.

The scenes from their marriage were infused with the anxieties and intimacies of staying together in what Libby calls "the splitting season." The scenes were played against a backdrop of love and fragility.

The Chapins have come a long way from the Nelsons.

In the early television days, when divorce was an accident and family problems a secret, couples on the tube were all permanently and perfectly mated. Dad might be a boob from time to time, and Mom might require a stroking or two, but marriage was a happily-ever-after, marred by only the mildest misunderstandings. Television contracts may have been short-lived, but the marriage vows never came up for renewal.

But sometime during the 1960s, divorce became the trendy, emotional Club Med. Singleness was where the action was and only a dreary slug would pass up a second chance for such a Creative Experience. Divorce became the Outward Bound of mid-life, Living Alone became the challenge. Splitting became the rite of passage that proved whether or not you had the right stuff. It was all, gawd help us, a growth experience.

It seemed that the very idea of creating a credible marriage eluded Hollywood, so the sitcom stars turned single. There was Alice, managing remarkably well on her minimum wage (did you ever get a look at that apartment?) and Ann Romano coping one day at a time without Mr. Romano. Even Larry said goodbye.

Most of the working marriages on the air took place during the Depression, on the prairie or in Bunkerville. But "United States" may just be heralding Stage Three.

This is the first evidence that the seismic shocks of the divorce statistics have hit the 16-inch world serials. When the Chapins fight, it is not assumed that they will make up and go to the seashore. When they hear about yet-another-separation they turn to each other and say, as Dick did, "How do you figure it? I thought they were happy." And they don't feel smug, just threatened.

The Chapins live in our era, when the ground is loose under permanence and security seems very shaky. Theirs are not the only children who wonder at every flare-up: does this mean divorce?

Yet in a peculiar way, this very anxiety has made marriage dramatic again. The taken-for-granted-marriage idea has been replaced by the marriage of high risks and high energy.

So far, "United States" is the most extreme example of life under the ax of divorce and covers of separation. But it is indicative of yet another change in attitudes.

In private lives, staying together has become news. Marriage -- this complicated, constantly questioned state -- has become a kind of challenge. And living together legally is a test of survival.

The Chapins hold back nothing. They talk and talk and talk about sex, money, the fear of missing something, the fear of being known -- the melting pot of anxieties in marriages lived as an alternative.

"You don't think there is a man alive that doesn't secretly wish we could be as untied as he once was?" says Richard.

"Yes, I can imagine wanting to be free of that one person who knows you so well," Libby answers. "How marvelous it would be to start all over with someone else. A perfect stranger with whom he can be an absolutely perfect stranger."

They may not last, this couple. They are excessively verbal, too honest, too wounded and wounding, too open about all of their fears, which are all of our fears. They may not be able to carry on week after week.

But that, after all, is the point.