It’s rather amazing, and not a little sad, that Eugene Levy, who’s so amusing in Christopher Guest’s ensemble pieces, has been almost unbearable in lead roles. Perhaps it’s just a matter of too much of a good thing. But whatever the reason, Levy is no more successful in “The Man” than he was nearly twenty years ago when he co-starred with John Candy in “Armed and Dangerous.”

Of course, maybe it’s just that the script here is no better than the one for that terrible 1985 movie. What Jim Piddock, Margaret Oberman and Stephen Carpenter have concocted is an example of a venerable genre, the mismatched-buddy action comedy, but one that’s produced more than its share of stinkers. The picture is less like “Midnight Run” or “48 Hrs.” than “Pure Luck.” Levy plays Andy Fidler, a preternaturally uptight salesman from Wisconsin who comes to Detroit to deliver a speech at a dental-supply convention, only to be sucked into a sting operation being conducted by gruff ATF agent Derrick Vann (Samuel L. Jackson). Vann, the typical rogue lawman whose dirty partner has just been killed during a weapons robbery (of course), has arranged to meet incognito with the thieves as a prospective purchaser of the guns they stole. Unfortunately, Fidler is mistaken for him by the crooks, and so Vann compels the hapless guy to continue the imposture in order to close the case, get back the merchandise, and clear himself in an investigation being conducted by an internal affairs officer (Miguel Ferrer) who suspects that he was in on the heist, too.

Everything that flows from the lame initial premise is flat and predictable. The incompatible duo bicker their way through all sorts of adventures, with Levy doing his prissily precise shtick and Jackson embarrassing himself with a caricature of the tough cop, until they inevitably bond (in one mawkish aside, Fidler helps Vann reconnect with his estranged wife and neglected daughter). Some of Levy’s bits would actually be pretty funny in three-minute sketch doses, but when strung together his cartoonish act grows tiresome. And even someone as expert as Jackson can’t do anything with the one-note Vann; after all, what actor, however fine, could cope with the illogical role of a supposed undercover agent who, when confronted by some Detroit police, flashes his badge in the middle of traffic and loudly announces his federal status to the whole city at the very time he’s trying to fool the bad guys into thinking he and Fidler are fellow crooks? The sense of desperation becomes most evident, however, when the script resorts to the lowest forms of flatulence humor in a vain attempt to elicit laughs–a motif that demeans both the stars. But Levy and Jackson aren’t the only performers who fare badly because of the lame writing. Luke Goss is trapped in the cliche role of a Euro-villain, Ferrer harumphs and glowers his way through the stock part of the hard-nosed IA investigator, Susie Essman is typically stern as the lieutenant troubled by Vann’s recklessness, and SNL’s Horatio Sanz stumbles and mumbles as the evidence-room sergeant whom Vann regularly shames into giving him confiscated cash for his off-the-record undercover operations. But nobody comes off as badly as the talented Anthony Mackie, who’s reduced to doing a crude stereotype as Vann’s reluctant snitch, named–of all things–Booty and forced to snivel and whine every time the cop thrashes him to extract information.

Through everything the direction by Les Mayfield (“Encino Man”) is pallid at best, bringing little energy even to car chases and shootouts and often leaving the actors looking positively stranded. On the technical side the movie is equally mediocre, with the Motor City setting seeming a case of the yin and yang of the universe. Not long ago “Four Brothers” used actual Detroit locations beautifully to create a palpable sense of place; even the grim backgrounds were distinctive and cooly eye-catching. The city in “The Man” looks like everywhere and nowhere, a dull, anonymous place–which probably stems from the fact that the picture was actually shot in Toronto. But that’s only fair, because this is one dull and anonymous movie. The only really praiseworthy thing about it is that it’s also one of the year’s shortest–less than eighty minutes when one subtracts the final credits. It just seems much longer.