At this rate, Chris Rock might never headline a good movie … unless it’s a concert film of his stand-up act.

The talented comedian hasn’t yet found a way to translate his uproarious, stinging social commentary into a cinematic mouthpiece. It’s not that he’s gone out on a limb and failed, it’s that his aim has been so low to begin with.

Previously, you could fault a poor choice of filmmakers and scripts for inexplicably lame efforts such as “Bad Company,” “Pootie Tang” or “Jay and Silent Bob Strike Back.” Now with “Head of State,” Rock has no one to blame but himself. He co-wrote it (with fellow “The Chris Rock Show” scribe Ali LeRoi) and he makes his directorial debut.

The result is a semi-funny idea (black guy runs for president) that is executed poorly. This political comedy is about as convincing as a campaign promise, and most of its jokes have been around longer than Strom Thurmond.

You know where things are going when a film’s funniest moments involve elderly white people kickin’ it to hip-hop music.

Rock plays Mays Gilliam, a heroic D.C. alderman who is recruited by the left to be the presidential nominee after the death of its frontrunner in a plane crash. The party’s plan is simple: If you can’t win the election, at least choose a candidate who will gain you credibility in future elections.

An upstanding minority candidate like Gilliam is perfect, as long as he tows the party line. (One of his aids hands him a card prior to a fund-raiser, saying, “Here are your off-the-cuff remarks. Learn them.”) But Gilliam believes he can actually win, so he starts creating his own urban platform aimed at appealing to the average Joe.

There are stretches during “Head of State” that hint at its potential. While campaigning and debating, Rock’s character makes several street language-laced rants against the system that have impact.

He asks what’s wrong with society when, “schools have old-ass books but brand new metal detectors?”

These moments are desperately needed in a film that lacks momentum. While they never quite work up the angry truth of similar ones spouted in the superior “Bulworth,” they at least give Rock a stand-up style platform to vent his considerable skill with words.

Also good is Bernie Mac, who plays Gilliam’s bail bondsman brother and eventual running mate. The energy level rises whenever the burly sitcom star appears, especially when he gives an interview explaining why someone in his profession is perfect to help “bail out” the country.

Other decent actors keep the thin plotline from totally derailing. Reliable thespians Dylan Baker (“Happiness”) and Lynn Whitfield (“Eve’s Bayou”) effectively portray Gilliam’s managerial staff. And Nick Searcy is amusing as his Southern-bred, right-wing opponent, who spouts the campaign catch phrase “God bless America … and no place else.”

Of dubious note is former Mike Tyson sparring mate Robin Givens, who appears as the gold digger girlfriend that Gilliam is dumped by before he gets famous. You’d be hard pressed to uncover a worse performance by a name actress than the one given by Givens. It’s a shrill, overbearing stereotype that must be seen to be disbelieved.

There are occasional moments of humor in “Head of State,” but the ratio is about one for every 10 jokes attempted. The overall sloppiness of the plot (what happens to Gilliam’s Black Muslim bodyguard?) and repetition of the gags (“Security!”) grow taxing even for a throwaway comedy — and a really short one at that.

Rock needs to find a movie outlet that can play to his substantial strengths. And he needs to do it quickly before he becomes the comedic equivalent of Michael Dukakis.