Centerpiece of the festivities is the innocent, tragic figure of the president's wife, with her mesmerizing baby-doll voice and a sincerity that would do a Stepford Wife proud. She's young, elegant, kind -- an American brand of aristocrat, identified not with privilege but with democratic ideals. Banished from her story is any hint of the Vietnam War, of marital infidelity, even of that dark day in Dallas on November 22, 1963. Only a cad could fail to love this icon of American modernity and class.

As the exhibition's wall labels point out, the 31-year-old First Lady elect (the youngest ever) "came to the White House determined to transform it into a theater of culture and taste," and in a scant three years succeeded in creating "a living museum of presidential history in which to celebrate American arts and letters."

Jackie appointed the first White House curator and established a committee of advisors to acquire period furnishings, paintings and objects, many of which had historical connections to previous tenants of the executive mansion. She told Life magazine that "It would be sacrilege merely to redecorate it -- a word I hate. It must be restored, and that has nothing to do with decoration. That is a question of scholarship."

The exhibition is a presentation of the Met's chic but curatorially suspect Costume Institute, and fills not the department's dank basement galleries but rather the expansive, second floor Cantor Exhibition Hall. There, the show is brilliantly installed by Vogue editor Hamish Bowles, who clearly knows the seductive ways of the window-dresser's art. One of the Met's picture galleries becomes, with the help of a painted, curved backdrop, a stage set of the White House Blue Room. Another gallery is decorated with faux Federalist columns. Everywhere lighting is low, and displays are spotlighted in the best treasure-house tradition.

Highlights of the show include many of Jackie's iconic outfits -- the pillbox hat from Bergdorfs that she wore to the inauguration, the gowns she wore to state dinners, the Oleg Cassini outfits that soon became the Jackie Look. Among the scant artworks is a drawing by Jackie herself, quaint and charming, and an 18th-century painting of Figures Preparing for a Hunt, complementing a photomural of Jackie on horseback and some riding costumes. In another gallery is some West Virginia glassware, with a copy of the Hillbilly News touting the First Lady's endorsement of the local product.

Curiously, as a fashion show, the exhibition represents a rather stodgy Jackie. Oleg Cassini's early '60s signature style was actually baggy and potato-sacky, with lots of big buttons and Easter pastels. After all, she was a young woman who had to appeal to 60-year-old statesmen. She only got hip much later, when she married Aristotle Onassis and could relax a little. But even in Washington, D.C., her evening gowns were undeniably elegant and timeless. Jackie had such good taste that her clothes would be wearable in five years (and were -- she was known for her parsimony).

The exhibition also includes a surprising range of memorabilia, especially for an art museum. The walls of one gallery are given over to blowups of the seating charts of state dinners. Another case holds printed matter from the inauguration -- a typescript of Jack's speech, Time magazine covers, an inaugural ticket, invite and program, an Oleg Cassini sketch of Jackie's ball gown.

More interesting historically are the handwritten notes that Jackie would send to heads of state on various benefactors. "I can NEVER EVER thank you enough for twisting Boudin's arm and making that enchanting brilliant man come to Washington," she wrote to Jayne Wrightsman (a celebrated collector and Met trustee) about the Paris decorator Stéphane Boudin, who helped her redo the White House State Rooms. The show even includes a pair of Jackie's sunglasses, as if to presage her later superstar look.

The show is so enchanting that it's easy to forget the compromises that it represents in the museum world, conflicts that are not new but that are seldom so obvious. Tonight, the exhibition is the setting for a party of the rich and powerful, as the Met hosts its annual Costume Institute gala, a milestone of the New York "social season." (The show is underwritten by L'Oreal -- a makeup company whose slogan is "I don't mind spending more for L'Oreal, because I'm worth it!" -- and Condé Nast, which of course publishes Vogue and other fashion titles).

Just as Jackie -- and American culture -- deftly invented a slick Town and Country ambiance to promote U.S. political and economic interests, so the Met's exhibition heralds not only that romantic legacy but the place of power in American esthetics. It played well in the halls of state as well as on television back in the 1960s, and it plays well in museum galleries now.