C-

Even Frank himself would blanch at this serving of stale, sodden Capracorn, another in the long line of phony Hollywood tales of American political uplift that stretches back to “Mr. Smith Goes to Washington” and beyond. Despite its title, in fact, Joshua Michael Stern’s broad, simple-minded movie might well have been called “Mr. Johnson Goes to Vote.” Stern previously made the rather precious (and, unless I’m mistaken, unreleased) magical fantasy “Neverwas,” and that picture, with all its flights of fancy, was much more grounded in reality that this superficially less far-out one.

The utterly implausible premise has the presidential race between Republican incumbent Andrew Boone (Kelsey Grammer) and Democratic challenger Donald Greenleaf (Dennis Hopper) come down to the electoral votes of a single state—New Mexico, where the two have tied. The deciding ballot will be cast by beer-guzzling good-ole-boy Bud Johnson (Kevin Costner), an apathetic layabout who’s just been fired from his job at an egg factory—quite justifiably, as he’s irresponsible and clumsy.

The explanation for his special status is that his irritatingly precocious daughter Molly (Madeleine Carroll) is so into politics that when her drunken dad failed to show up at the polling place, she tried to vote in his place—unsuccessfully, because the machine was unplugged halfway through the process, but under state law the glitch allows him to cast his ballot again. What follows is a full-court press by both Boone and Greenleaf, accompanied by their unprincipled advisors Martin Fox (Stanley Tucci) and Art Crumb (Nathan Lane), respectively, to secure his vote by virtually any means possible, short of outright bribery (though even that’s considered, briefly of course—we’re supposed to sort of respect these candidates, though it’s hard to see why). Bud’s failure to take his duty seriously and his willingness to bask in the publicity sour his relationship with his daughter, while pretty local reporter Kate Madison (Paula Patton), whom Molly sees as a surrogate mom (and a possible mate for Bud), uncovers the truth about how his vote went uncounted and must decide whether her career is more important than being a nice lady.

There are a few amusing moments in “Swing Vote”—most notably the two pandering commercials that liberal Greenleaf makes to bring him into line with Bud’s supposed views—one on illegal immigration, the other on abortion. (The one starring Boone, in which he switches his position on gay marriage, is much less funny, trading on the crudest stereotypes.) But otherwise the quality of humor is lamentably lame. A particularly clumsy bit comes when the president introduces Bud to the old nuclear “football” suitcase to demonstrate the commander-in-chief side of his office—a symbol that was certainly central to Cold War days but, in the present age, seems close to an irrelevancy. Boone and Greenleaf are both such spineless goofballs that it’s laughable when they’re described as extraordinary toward the close, and it’s impossible to believe that a preening poseur like Grammer and a seedy weirdo like Hopper could ever be serious candidates under any circumstances. (They’re nearly as absurd as creepy William Hurt was as the chief executive in “Vantage Point.”) As their manipulative advisors Lane and Tucci get little opportunity to shine—I counted precisely one decent line of dialogue for each of them. And the dumb-bell shenanigans of Judge Reinhold and Charles Easton as Bud’s buddies are positively dreary. As satire, “Swing Vote” is even more toothless than “Dave” was.

But all that’s secondary to the shallowness of the stuff at the center of the picture that’s supposed to humanize the story. Costner works hard to make Johnson a likable lug, but Bud remains less an everyman than a rightful nobody, and as his daughter Carroll comes across as probably the most priggish example of juvenile rectitude since the doomed boy Haley Joel Osment played in that piece of didactic claptrap, “Pay It Forward.” Their loving relationship is of the falsest kind; indeed, the only authentic moment comes when Molly runs off to her long-absent mother, who’s played by Mare Winningham with a frightening intensity that makes her brief scene very impressive (but, unfortunately, out of place in the bland surroundings).

And the picture saves the worst for last, ending with a long, bathetic speech by old Bud confessing his own failings and extolling the importance of participating in the electoral process—and this at the beginning of a candidate debate, where he leaves the two contenders waiting (and listening) sheepishly as he drones on and on and…on. It’s basically a filibuster though, unlike M. Smith, he’s not in the Senate.

Meanwhile the wafer-thin journalistic subplot gives the attractive Patton little to work with, and George Lopez should have been advised to tone things down as her career-obsessed boss—just another miscalculation on the part of writer-director Stern. There are a few cameos by celebrities supporting one or another of the candidates (Willie Nelson, Richard Perry) or commenting cynically about Bud (Bill Maher), to little comic effect, and many more by TV newspeople whose presence is intended to give a feeling of verisimilitude to the plot. They’re all embarrassing, but Chris Matthews is especially so (probably because he’s onscreen the longest), though Larry King (who’s been mercifully absent from the screen lately) shows up to deliver the single most asinine line of dialogue assigned to any of them. It seems to come quite naturally to him. Technically the movie is okay, but nothing special.

Hollywood has made solid political satires in the past—“Wag the Dog,” “Dick” and even Gore Vidal’s “The Best Man” come to mind, and of course “Dr. Strangelove” sets the bar as high as can be. If this flabby piece of whimsy is the best the studio system can offer for the election of 2008, our American democracy is in a truly sorry state.