Ask Rosie O'Donnell's to play favorites with this year's Tony nominees, and mum's the word. As the hostess (and a producer) of the Tony Awards, O'Donnell is too much of a class act to tip her hand about which shows she's rooting for out of the dozens that opened during the 1997-98 Broadway season.

However, she admits that her three-year-old son has a stated preference for The Lion King, which he's already seen three times, accompanied by mama Rosie. "Parker just loves it," she says. "Whenever I put on the movie video, he says, 'Let's go see the show.'" Her new daughter, Chelsea, is too young for a theatre outing, but is there any doubt that, in the O'Donnell household, learning about Broadway is ranked up there in importance with learning how to walk and talk?

Since her phenomenally successful, Emmy Award-winning TV show, "The Rosie O'Donnell Show" premiered almost two years ago, O'Donnell has rightfully earned a national reputation as Broadway's biggest fan. Her show is a major pipeline of national promotion for shows on the Great White Way, and her commitment to using her syndicated daily talk show to spread the word about Broadway to people west of the Hudson has made O'Donnell a major force in the theatrical community.

"Rosie is about as effervescent a theatre fan as you'll find, and she has an extraordinary number of viewers with which to share that excitement," says Michael David, a producer of Titanic, which O'Donnell championed last year after it opened to lackluster reviews. It went on to win five Tonys, including Best Musical. "She expands word-of-mouth exponentially, but more than that, she can't be bought. Because Rosie speaks from the heart, her audience trusts her, and her enthusiasm becomes therefor all the more infectious."

O'Donnell wouldn't have it any other way. "Theatre is the only area of entertainment that eats its young," she says. "The critics seem to be out get you, and I don't understand it. If we don't encourage and support new shows, doing everything we can to insure that they survive, we're not going to get the next generation of Sondheims." The make-or-break power of her opinion is not something she set out to achieve, the way a critic might. "I think of it as fair payback for all the joy Broadway has given me, all the solace in my career and life. I'm very touched that I can, in some way, make a difference to Broadway, because Broadway was what really inspired me to be a performer."

It was an early calling. There's still a lilt of pride in her voice when she confesses that she was the only second grader at her Commack, Long Island elementary school who knew all the words to South Pacific and Oklahoma! Perhaps that's why O'Donnell stresses the importance of nurturing the youth market. "If children see a Broadway show at 10 or 12, they'll get that theatre bug and then we'll have a whole new generation to support Broadway."

O'Donnell still wins the prize when it comes to knowing the scores to shows, both famous and obscure. It has served her well on her talk show, where she often breaks suddenly into a forgotten show tune without missing a beat -- or a word -- always accompanied by John McDaniel, her musical director and amiable second banana.

"McD," as O'Donnell calls him, is her musical theatre match. They made their Broadway debuts together in the 1992 revival of Grease!, and hit it off so well that O'Donnell invited McDaniel to be "The Rosie O'Donnell Show"'s music man. Their on-camera rapport is one of the show's appeals, and McDaniel insists that it's 100 percent genuine.

"I'm crazy about her," he says, "and I'm so proud of what she's doing for the theatre. It's so much fun to celebrate Broadway with Rosie because she just lights up." McDaniel describes O'Donnell's love for Broadway as "a kid in a candy store." "No television personality has been this supportive of the theatre since Ed Sullivan, and even he wasn't as excited and passionate about Broadway as she is."

Last year's announcement that O'Donnell would host the broadcast was accompanied by two other bold new strokes by the Tony Awards: The change of venue to Radio City Musical Hall, and the unprecedented two-network arrangement whereby PBS broadcast the first hour of the awards (interspersed during its documentary, "Broadway '97: Launching the Tonys") and CBS broadcast the remaining two hours. The results? One of the best Tony Awards shows ever,

Though she appeared only briefly on the PBS portion of the show, O'Donnell greatly appreciated the contribution of "Launching the Tonys," which provided interviews with the contenders and insights into the kind of theatre magic that they made to earn a Tony nomination. "I'm very pleased that PBS is doing it again this year," O'Donnell says. "I think it added a lot to the show, and the additional time it afforded allowed all the winners do their thank-yous in an emotional, unhurried fashion. I think that this combination of the two networks insures the Tonys' longevity on broadcast TV."

Anyone who saw the opening number of last year's Tonys -- and millions of viewers did -- knows that O'Donnell would love to be back on the boards, singing and dancing and stopping a show. Unfortunately for theatre-goers, being a working mother with a hit TV series rules out an immediate return to Broadway. "While the TV show is on," says O'Donnell, "it would be physically impossible, because of the amount of work and energy it takes to do a Broadway show eight times a week." Indeed, O'Donnell has been taping two-episodes-a-day of "The Rosie O'Donnell Show" to "steal" nine weeks so she can do a movie in Ireland -- The Mammy -- co starring Brenda Blethyn (Secrets & Lies) and directed by Anjelica Huston.

Farther down the road is the movie version of Chicago, which Larry Gelbart is adapting for Nicholas Hytner to direct. O'Donnell has long been rumored to play prison matron Mama Morton to Goldie Hawn and Madonna. "I don't think Chicago is in shooting shape yet," she says. "If it's delayed until next summer, there's a good chance I'll do it. I certainly would love to."

Meanwhile, the Emmy-winning "The Rosie O'Donnell Show" is going strong, complete with an in-studio baby-room."I got the kids with me at work," she says. "I can't sparkle without them."

The kind of family atmosphere that O'Donnell's on-air anecdotes about her children provide allows her legions of fans to feel like part of her family. And that's why a passing plug by O'Donnell can cause a quake at a Broadway box office: It's like a dear friend called up and said, "You have to see this show. It's not to be missed!"

-- By Harry Haun