The concept of reuniting Robin Williams with his “Good Morning, Vietnam” director Barry Levinson sounds like a comic natural.

But cast back for a sec. Despite Williams’ sometimes inspired riffing in that movie, “Good Morning, Vietnam” had a pretty serious focus.

Turns out Levinson and Williams are up to similar business in “Man of the Year.” In this one, Williams plays a comedian whose impromptu presidential campaign somehow vaults him into a victory on election night.

Levinson seems inspired by the way show biz has overwhelmed politics in recent years, to the point where the thought of a late-night comedian, a la Jon Stewart, being swept up in the process isn’t so far-fetched. Great possibilities here, right?

And yes, there are some healthy chuckles along the way, most of which sound improvised from Williams’ stand-up routines. Much of the movie consists of Williams standing in a room cracking wise while his campaign associates (Christopher Walken and “Daily Show” commentator Lewis Black) laugh.

The problem is, Levinson wants to make a suspense movie, too. This involves an employee (Laura Linney) at a massive computer corporation who tries to blow the whistle after she discovers a flaw in the company’s computer-voting system. That’s the same system that will be used in the presidential election. Uh oh.

Anybody going to “Man of the Year” for a little satirical fun will experience a creeping sense of disappointment as it becomes clear the movie wants to be taken seriously. Even Robin Williams looks tighter than ever; he’s never been less liberated in his comic style.

Meanwhile, Linney’s horribly misconceived role strands the fine actress somewhere between screwball comedy and a psychotic breakdown. Only Christopher Walken seems to be actually enjoying himself.

The blame has to go to Levinson, whose “Wag the Dog” was a funnier political picture (but just as sloppy). Gaps in logic abound, and the film has no grasp of what might actually work in a political campaign. And we never, ever know what motivates Williams to actually run for president.

Although “Man of the Year” acknowledges the potency of the new political humor, it goes all serious on us. Wrong move: What we need right now is another “Dr. Strangelove,” not another “Good Morning, Vietnam.”

Robin Williams stars in “Man of the Year.”