In "The Sentinel," bad blood between formerly friendly Secret Service agents David Breckenridge (Kiefer Sutherland), left, and Pete Garrison (Michael Douglas) perplexes rookie Jill Marin (Eva Longoria).

The casting of "Desperate Housewives" bad girl Eva Longoria as a Secret Service agent isn't the most preposterous thing in "The Sentinel." But it's close.

Yet, surprisingly, it doesn't much matter.

A routine yet diverting political thriller, "The Sentinel" is the kind of solid, middle-of-the-road movie Hollywood used to crank out with reassuring regularity -- but doesn't bother with much anymore.

It's got a capable cast and a crisp, craftsman-like look. And if it doesn't reach new moviemaking heights, that's probably because it's not aiming for them.

Instead, it settles for dependable, down-to-earth entertainment, nothing more -- and nothing less.

It's the kind of movie that, in days of yore, might have starred Kirk Douglas.

In this day and age, however, "The Sentinel" stars Kirk's son, Michael, who bridges the generations himself with a younger second-generation actor, Kiefer Sutherland.

Nobody would confuse Kiefer's father, Donald Sutherland, with the kind of two-fisted heroes Kirk Douglas -- or, for that matter, Michael Douglas -- played.

Yet, with his "24" TV training, the younger Sutherland has become just that.

Watching Douglas (as an under-fire Secret Service vet) and Sutherland (a friend-turned-foe) butt heads in "The Sentinel" provides the movie's most potent dramatic fireworks.

It also gives the movie a dramatic subtext that's a lot more credible than some of the machinations cooked up by "Ocean's Twelve" screenwriter George Nolfi, who adapts Gerald Petievich's novel.

Douglas plays Agent Pete Garrison, who "took a bullet for the old man" back when John Hinckley Jr. shot President Ronald Reagan in 1981. He's now assigned to First Lady Sarah Ballentine (classy, understated Kim Basinger).

When an all-too-credible assassination threat targeting the current president (David Rasche) surfaces, an old informant of Garrison's (Raynor Scheine) delivers even more shocking news: the plot involves someone inside the Secret Service.

As the hunt for the turncoat kicks into high gear, Agent David Breckenridge (Sutherland), who's got a longstanding grudge against Garrison, leads the charge, aided by rookie Jill Marin (Longoria).

Garrison's not the traitor, of course. But he's got a guilty secret of his own -- one that provides the perfect opportunity for the true guilty party to frame him.

The cat-and-mouse chase that ensues is hardly on a par with the classic adversarial dance Clint Eastwood and John Malkovich performed in 1993's "In the Line of Fire."

For one thing, Nolfi's screenplay doesn't provide clear or credible motivation for either the assassination plot or the traitor's involvement in it.

For another, "The Sentinel" lacks the character development and psychological depth that give superior thrillers their emotional heft and express-train momentum.

Director Clark Johnson ("S.W.A.T.") undoubtedly knows that. As an actor, Johnson starred in one of TV's all-time cop dramas, "Homicide: Life on the Street." (That's also where he cut his teeth as a director.)

If "The Sentinel" had half the smarts and depth "Homicide" displayed from week to week, it'd be a far better movie. Because it lacks those qualities, however, Johnson makes the canny decision to play "Beat the Clock," cranking up the pace to speed through the movie's Air Force One-sized plot holes.

In the process, Johnson stages a lot of chase sequences that feature striking visuals and insider stuff -- to say nothing of guys (and gals) in suits dashing to and fro, exchanging terse tidbits of information in between all those desperate wind sprints.

Throughout, however, "The Sentinel" counts on its mostly credible cast to deliver the goods. For the most part, they do.

Alas, Longoria seems totally out of her depth -- and, without the sassy brassiness of her TV vixen character, far less interesting as well.

But it's good to see such trusty types as Martin Donovan (as a fellow Secret Service agent), Blair Brown (as the president's national security adviser) and ex-"ER" regular Gloria Reuben (as an agent's wife) turn up in supporting roles.

The grizzled Douglas and the determined Sutherland, meanwhile, keep "The Sentinel's" true central conflict percolating -- and, in the process, embody the transition from one generation of heroes to another.

"The Sentinel" may not be all that it can be. But at least its leading men do their duty. And, these days, you can't expect much more.