Smart, sharp political satire it's not. But Chris Rock's "Head of State" -- the comedian's directorial debut in which he plays a black man running for president -- mixes a few stinging zingers into its generally crowd-pleasing brand of snickers and knee-slappers.

When asked if he'll step in for the Democratic candidate who died when his plane and his running mate's plane "crashed into each other over Virginia," Mays Gilliam (Rock), a Washington, D.C. alderman, has a split-second flash forward to being shot at his inaugural address before even finishing the line "My fellow Americans..." But he accepts the nomination anyway.

He's provided a specially trained, sworn-to-secrecy "super whore" -- a post-Clinton perk devised to help Democratic candidates avoid sex scandals.

"God Bless America, and no place else!" is the almost too accurate campaign slogan of his Bush-like opponent.

And even before the first line of dialogue, Rock gives a good-natured ribbing to Al Gore, Bob Dole, Hilary Clinton and several other politicians whose names appear large in the opening credits, followed by the words "...are not in this movie."

Most of the flick's ample laughs, however, come from much lower-brow gags like the sight of a fund-raiser full of aging, whitebread, plastic-surgery-scarred aristocrats doing the Electric Slide to rap singer Nelly's bump-and-grind anthem "Hot In Herre" -- and singing along.

But how does a small-time neighborhood representative from the D.C. ghetto ("I work in a neighborhood so bad that you can get shot while you're getting shot!") get tapped for a presidential run? Well, that's where the "Head of State" premise gets a little thin.

"We're gonna lose this one," says the politically ambitious party chairman played by James Rebhorn (Jude Law's father in "The Talented Mr. Ripley"). "We need someone who'll put on a show" -- and draw minority votes for his own White House run in 2008. Since no one with real presidential ambitions wants to play the patsy, Rebhorn and campaign managers Dylan Baker ("Changing Lanes") and Lynne Whitfield ("Eve's Bayou") dig up Mays.

But while Rock bats about .700 with a steady stream of laughs, as a writer-director he's clumsy at best. "Head of State" has little in the way of story arc, and instead jumps from unrelated incident to unrelated incident with the occasional pivotal line of dialogue thrown in.

"It just seems like I should be talking about something more relevant," Mays complains after a few weeks of shaking hands and kissing babies. Next thing you know, he's winging it at rallies ("How many of you work in a city you can't afford to live in?") and climbing in the polls with the campaign slogan "That ain't right!"

Rock spends far more screen time inside his campaign bus (which he had airbrushed to look like a rap group tour bus) than he does meeting and greeting at actual whistle-stops. He invents fictitious political rules (if he gets more than 30 percent of the vote, he'll supplant Rebhorn as the party's '08 front runner) and ignores real ones (he picks his bail bondsman brother -- played by the scene-stealing Bernie Mac -- as his running mate).

He slaps together a subplot romance with a working-class girl played by Tamala Jones ("The Brothers") that becomes a surplus aside without an ounce of chemistry or authenticity. And Mays himself is little more than an assemblage of a stock character elements -- a little bit of generic community activism here, a little bit of homeboy punch line there.

But for the most part, Rock's absurdist sense of humor ("Head of State" takes place in a world where rap radio stations interrupt the music for news reports then "return you to your Jay-Z song already in progress") saves the movie from its own shortcomings.

When turning on the political satire, Rock is often hilariously astute about things like negative campaigning ("Mays Gilliam, he's for cancer!" claims a TV ad). The movie's social satire is often even funnier. A crane shot late in the film shows panic in the streets of a gated suburban community when it's announced on the news that "a black man may become president of the United States."

Had Rock chosen to go deeper, smarter and darker instead of pulling punches to appease a studio looking for a PG-13 film for mass audiences, "Head of State" might have been a spot-on political farce instead of an unsophisticated lampoon with an unconvincing heart-felt speech finale.

But while this movie falls short of its potential, funny is still funny.