Dead presidents: one of Stephen Sondheim's darkest visions, Assassins is powerful and timely stuff, even in an uneven new production.

Assassins * Book by John Weidman * Music and lyrics by Stephen Sondheim * Directed by Joe Mantello * Starring Neil Patrick Harris, Michael Cerveris, and Denis O'Hare * Roundabout Theatre Company at Studio 54, New York City (through June 20)

In his leisure time Stephen Sondheim loves to play games and solve puzzles, and as a composer he has revolutionized Broadway theater by giving himself challenges that push the envelope of standard musical theater form. But of all his musicals to date, none has a more experimental narrative than Assassins, which was originally produced off-Broadway in 1990 and has just been revived on Broadway.

Its form is a series of sketches--there's no central story or character for the audience to follow. It's framed as a hellish carnival sideshow in which all time and space coexist. And its content is emotionally and politically provocative. Focusing on nine people who attempted to kill U.S. presidents (four succeeded, five failed), Assassins asks us to see them as a dark fun-house-minus-the-fun reflection of the American character. Instead of considering them aberrations, what if we considered the outrage, malevolence, and discontent of the people who commit politically motivated crimes--not to mention their goofiness, narcissism, and outright insanity--to be just as American as apple pie in the land of the free and the home of the brave? In other words, what if we looked at ourselves the way the rest of the world sees us?

There are so many ideas (comic, musical, and intellectual) flying around in Assassins, it's fiendishly difficult for the show to hang together. Alas, Joe Mantello's ambitious production for the Roundabout Theatre Company does not succeed in making it work. Staged at Studio 54 in the supper-club configuration that previously served the long-running revival of Cabaret, the show is hampered by an awkward and inappropriately casual relationship between the audience and the stage. The cumbersome set--a semicircular gallery underneath a spiraling section of roller coaster--sometimes obscures the performers. And the cast is a mixed bag.

The comic scenes in John Weidman's book play like gangbusters thanks to Mary Catherine Garrison, Becky Ann Baker, and Mario Cantone. The two women play, respectively, the Charlie Manson acolyte Squeaky Fromme and the huddle-aged mother of four Sara Jane Moore, both, of whom tried to shoot President Ford in 1975. Cantone's character, Samuel Byck, is a raving lunatic who sends taped diatribes to celebrities and attempts to hijack a plane and drop it onto the White House to kill Richard Nixon. (Hard as it is to believe, these are true stories!) Playing Charles Guiteau, the failed evangelist who killed President Garfield, Denis O'Hare lets his usually enjoyable mannerisms slide into shtick, while Alexander Gemignani is poignant as Reagan's assailant John Hinckley.

But the actors with the heaviest historical and dramatic chores don't cut it. Neil Patrick Harris's pleasant voice conveys the earnest, simpleminded mythifying of the faux-narrator character known as the Balladeer, but for him to morph into Lee Harvey Oswald requires a transformation that simply never takes place because Harris (who's been working hard to be known as something other than the former star of Doogie Howser, M.D.) lacks the dramatic chops to pull it off. And his insufficiency makes Michael Cerveris as John Wilkes Booth look bad and blustery in their climactic encounter.

Yes, a scene between Lee Harvey Oswald and John Wilkes Booth--the level of imagination Sondheim and Weidman poured into Assassins is terrific. The duet between Hinckley and Fromme, who sing "Unworthy of Your Love" to their love objects Jodie Foster and Charlie Manson, is one of Sondheim's most beautiful and tuneful ballads ever. And even though it doesn't quite come off in this version, Assassins is a tough, compelling essay on the gap between American ideals and American realities. Fascinating as it is to see and discuss, though, it's not exactly meat-and-potatoes theatrical fare. It will probably always remain caviar for the general.

Shewey writes on theater for The New York Times.