THREE DECADES AGO, JACQUELINE Bouvier Kennedy was belle of the ball at the christening of the Whitney Museum of American Art's modern headquarters in Manhattan. This year, JFK Jr.'s bride, Carolyn Bessette Kennedy, stole the show. At a Nov. 4 benefit marking the 30th anniversary of the Marcel Breuer building, the newlyweds made their first official public appearance. Even seen-it-all New Yorkers were wowed. "She's a swan," gushed cochair Barbaralee Diamonstein-Spielvogel. "She's handling the attention very well."

No small task, that. From the moment she stepped out of a chauffeured car with the sexiest spouse alive, the elegant Carolyn was besieged. Waiting for her at the museum's entrance were paparazzi including Ron Galella, the cameraman Jackie O once took to court. Dressed in a slim Prada coat and simple calf-length gown (both black), Bessette Kennedy, 30, gripped the hand of her 35-year-old hubby while flashes exploded in their wake.

Inside, where such patrons as architect Richard Meier and a showbiz stray or two (like actress Liv Tyler) chatted over roast chicken, Carolyn made confident small talk with other guests and, at the center table, threw an arm across the back of John's chair. "She's very sexy, nice and cool," said a guest who schmoozed with her. Added cosmetics mogul Leonard Lauder: "John was worried she would be over-whelmed, but she's a pro."

Though some sniped about her dress ("She doesn't look any different than 27 other blondes in this room," shrugged designer Arnold Scaasi), most had only praise. "She's very elegant," said designer Miuccia Prada. JFK Jr. seemed firmly in her thrall. When the evening ended, he dived to fetch the purse that slipped to the floor. "He crawled underneath the table," purred Lauder's wife, Evelyn. "How gallant."