Fred Claus, a likable slice of candy-colored Christmas schmaltz, is the ultimate test for the Vince Vaughn persona. In the midst of the fine-tuned family friendliness of Cars scribe Dan Fogelman's script, Vaughn remains obstinately himself: a lanky assembly line of asides, quips and sarcastic digressions that ping-pong off each other with maniacal energy. It's hard to imagine many children finding these labyrinthine runs funny -- Vaughan's references range from Jim Jones to Patty Hearst -- but Fred Claus is nevertheless a bid for broad bankability, an attempt to prove that his shtick will work outside of the 18-35 year old demo that pushed Wedding Crashers past $200 million.

It's the same move that thrust Will Ferrell to stardom with Elf. But where Ferrell tweaked his character to become more childlike and broadly appealing, Vaughn doesn't deviate one iota from his persona; Fred Claus is the same acerbic schlub that appears in Old School, Dodgeball, Wedding Crashers, and The Break-Up. The film's tone is schizophrenic as a result, alternating Vaughn's sophomoric ramblings with gauzy sentimentalism. The latter eventually wins out.

This latest iteration of the Vaughn persona lives in Chicago as a repo man, swiping flat-screen televisions from pre-teen girls while schooling them on the joys of college-age motherhood. The reason he's so bitter? His brother is Santa Claus (Paul Giamatti), and that is one rotund shadow to live in your whole life. As a result, his only gift to mankind is a massive inferiority complex and the urge to buy an Off-Track Betting site. He has to borrow 50 grand from St. Nick to get it off the ground, so he flies on up to the North Pole (abandoning his girlfriend, an unnaturally attractive traffic cop played by Rachel Weisz). As it turns out, Santa has some worries of his own, mainly in the guise of an efficiency expert (Kevin Spacey) who is threatening to outsource his job to (gasp!) the South Pole. Giamatti plays St. Nick as a brow-beaten, tightly wound husband with body-image issues. He's more Ralph Kramden than rosy-cheeked icon.

The cast reads like an after-party at the Independent Spirit Awards -- along with Giamatti, Spacey and Weisz, there's Kathy Bates as the super-judgmental Mama Claus, Miranda Richardson as the haughty Mrs. Claus, and, Break-Up alum John Michael Higgins as the head elf, Willie, who ushers Fred around town and harbors a gnome-sized crush for the short-skirted and full-size assistant, played by Elizabeth Banks.

Director David Dobkin (reuniting with Vaughn for the third time after Clay Pigeons and Wedding Crashers) affords his star plenty of room for improvisation, but proves adept at the comic montage as well. Building on the propulsive wedding reception sequence in Crashers, here Dobkin offers up a swiftly edited chase scene -- a Keystone Cops group of Salvation Army Santas running Fred down after he swindles a handful of donation money from shoppers. The jolly ones get hit by cars, confused on escalators, and smacked in the face with yellow warning signs with a speed and discombobulated grace worthy of a Mack Sennett short.

Unfortunately, Dobkin's faults also carry over from Wedding Crashers, which quickly lost steam under the heavy-handedness of the central romance (recall Owen Wilson’s bathetic beachfront flirtation with Rachel McAdams). The same holds here: the central dramatic arc of the brotherly friendship renewed (and secondarily, of Spacey’s learning not be a mean bastard) rings indelibly hollow.

Fred Claus strains to fulfill its generic expectations with lumbering scenes of saline tears and elfin togetherness. Its most successful moments are of the throwaway variety -- the richest gag occurs at a "Siblings Anonymous" meeting that contains the greatest cameo performances of the decade -- but they are always followed by a doleful return to conventions. Vaughn is not much of a dramatic actor, and his sudden conversion into a bland nice guy after learning supposedly important lessons about responsibility robs him -- and the film -- of his charm and most of his talent.