If ever this country needed a politician with courage, talent and the ability to spell out the difference between platitudes and truth, it's right now. So what could be better than a film with the smooth but straight-talking Chris Rock to spell it all out for us?

Unfortunately, "Head of State," which he co-wrote and directed in addition to starring in, is not that vehicle. We can forgive the tired plot, in which Rock, as Washington, D.C. alderman Mays Gilliam, is chosen to run for President in 2004 after the (unnamed) party's candidate and his vice-presidential running mate have died in a plane crash. Mays is chosen because he'll be a sure loser, allowing the party's unscrupulous head (James Rebhorn) a clear field for 2008. And when the predictable happens and Mays takes charge of his own campaign and begins speaking out, the voters respond enthusiastically and - well, you can guess the rest.

The problem is that Rock's straight talk is just as vapid and mealymouthed as his opponent's, with no meat on its bones and no truly populist positions. "That ain't right!" is the phrase that everyone picks up on after his recitation of what's wrong with ghetto schools, poor public transit, and lack of decent-paying jobs. Well, that ain't right, but stopping there is not what a president should do. Rock's unwillingness to offend anyone just drains his film of any power.

Oh, and it's supposed to be a comedy. Rock's script has occasional moments, left over from his standup act, but he misses a great opportunity here to work with Bernie Mac, who appears as Rock's older brother Mitch, a bail bondsman from Chicago, who becomes his running mate. They should strike sparks off each other, but seem barely to be nodding acquaintances.

At the beginning of the film Mays is engaged to the bitch of all time (Robin Givens, overacting shamelessly), who dumps him when she thinks he's on the skids. But of course, this being the movies, he finds a better love in the quick-stop gas station attendant played by Tamala Jones, while fending off the insistent return of the now fawning Givens. It becomes embarrassing to watch.