A month ago, ABC's divorce drama Once and Again was celebrated as the season's strongest new show-boosting ratings not only for ABC, but also for the Lifetime cable channel, which rebroadcasts each Tuesday's episode on Friday nights. It was so popular that ABC (briefly) considered moving aside its veteran hit, NYPD Blue, to give Once and Again its coveted time slot. Critics applauded Once and Again's "realism," and newspapers did stories about a new acceptance of "non-traditional" families. But the thrill is gone. Not even following the scholastically challenged but addictive Who Wants to Be a Millionaire helps the show; last week, Millionaire won its time slot, but viewers didn't stick around to see Once and Again's Lily and Rick fool around with each other and their children's lives. Ironically, the realism is what's behind the ratings plunge. In one way, at least, Once and Again is true to life: Divorce, and relationships after divorce, are messy, exhausting things. The show retains some of the sticky-sweet romance it began with. In one episode, Lily (Sela Ward) pouted at having to leave her new boyfriend for a business convention: "I can't do this! Forty-six hours is too long! Can I take your blue sweatshirt and your smell with me?" Lily's a newly separated mother, raising two daughters. She has an inexplicably great job-on a bookstore clerk's wages, apparently, she can afford the sparkling new SUV, the L.L. Bean wardrobe, and the house in a better suburb. Rick is a single father, divorced, and juggling custody with his ex-wife. We learn their stories not only from the plot but also from the truly annoying cut-away black-and-white interviews (a stylistic device nicked from bank commercials). Mostly, we learn that Lily and Rick embody some of the worst parenting practices around. A recent episode revolved around a high-school party; Rick gives his son permission to go, even though he knows there's going to be underage drinking, illegal drugs, and no supervision. He has a twinge of guilt, but it doesn't last. He remembers his own father's strictness. "My father generally terrorized us," he says in one of those cut-away interviews. "He'd sit there with a scotch, and generally showed us he didn't trust us." The party turns out as expected-drink, drugs, police, and a 15-year-old hospitalized for alcohol poisoning. Rick's son, who had promised not to drink, is plastered. Rick's response? He laughs, and tells his unseen interviewer about the wild parties he went to in his youth. "So now, I'm supposed to be a hard-ass?" he asks. "After what I've done?" That's a pretty common refrain these days-parents feeling that because they've made mistakes, they don't have the moral authority to steer their kids away from those same mistakes. Lily's daughter also went to that party. Lily's response was an angst attack about her child not being properly supervised. Her sister's words of wisdom for her? "You can't protect her from everything that's out there"-so don't even try. At heart, though, Once and Again isn't really about parenting, or even bad parenting. It's about sex. "Can we make a deal?" Lily asks Rick. "When we're in bed, not to mention our kids' names?" Narcissism at its best-and nobody wants to see that. NYPD Blue has nothing to worry about.