First, a clarification: Despite its title, and Hollywood’s ever-increasing hunger for horror revivals, this new “The Sentinel” is not a re-imagining of the 1977 schlocker starring John Carradine as a blind priest who lives in a Brooklyn brownstone and guards the gate of hell.

Too bad.

Instead, this movie stars Michael Douglas, all Kevlar and wattles, as living legend Pete Garrison, a stalwart Secret Service agent who took a bullet for Ronald Reagan and is now protecting President John Ballentine. Never mind that bodyguards are generally supposed to be younger than the adults they’re guarding. Garrison is not a by-the-books kind of guy.

Which is perhaps why he’s also bedding the first lady.

But then Garrison starts getting blackmail threats. The president starts getting assassination threats. And Garrison’s best friend in the Service, David Breckinridge, begins to suspect there’s a traitor in the organization – a traitor who, according to the evidence, looks a lot like Pete Garrison.

Can you smell a setup?

You can sure smell something, and it’s not cherry blossoms. Although the screenplay is based on a book by Gerald Petievich, the author of “To Live and Die in L.A.” and a former agent, nothing besides the daily details rings true. The confrontations and conflicts feel forced. The characters are mere constructs. And as for the “surprise” villain – well, remember, always suspect the best-known actor with the fewest lines.

The plotting isn’t the only thing showing its age. Douglas has a full head of slicked back Gordon Gekko hair and, whether by good genes or sharp scalpels, his face doesn’t automatically give away his years. But he still turns 62 in a few months, and the camera suspiciously speeds up whenever he has to throw a punch.

Since Douglas cast himself – he’s also one of the movie’s producers – it’s easy to understand why no one tried to talk some sense into him. But someone needs to. He’s supposed to be playing Kiefer Sutherland’s colleague; instead, he looks like one of Donald’s.

Everyone else plays their assigned roles. Sutherland, who revived his career playing a nervy federal agent on “24,” returns to the big-screen playing … a nervy federal agent.

Eva Longoria, who shot to fame playing a snippy, man-bait Latina on “Desperate Housewives,” takes on her first big movie role playing … a snippy, man-bait Latina.

What’s particularly disappointing is that there are good movies to be made about the Secret Service, particularly in this age of national paranoia. “In the Line of Fire,” which starred Clint Eastwood in 1993 and faced the age issue head-on, should be the model.

But that movie was directed by the talented Wolfgang Petersen, not the tractable Clark Johnson, a TV hack whose only previous theatrical feature was the forgettable “S.W.A.T.,” and whose idea of style is limited to bright colors and blurry graphics.

And that earlier movie had a smart plot, and John Malkovich as a clever villain – not muddled stuff about former Soviet republics or British-accented Euro-trash bad guys.

For all its nonsense, though, “The Sentinel” does teach a few lessons. Douglas is best when he dares to act his age (as in the shaggy, sloppy “Wonder Boys”).

Sutherland and Longoria should read something besides the pay stub whenever they’re choosing a movie to do between TV episodes. Presidents should probably not employ bodyguards who are also guarding the bo]dy of the first lady.

And if you’re going to make a movie with the same title as a second-rate horror film, it should be at least as entertaining as that second-rate horror film.