Is ''Star Wars''' reign about to end?

After two weeks as the No. 1 movie in the country, ”Star Wars: Episode II” faces perhaps its toughest new competition with the arrival of Ben Affleck’s disaster thriller ”The Sum of All Fears.” In other words, this could be a close one.

For ”Star Wars,” this third weekend is extremely important, as it will indicate more clearly where the film is headed in terms of final domestic box office. After a comparatively large 41 percent drop from week one to week two, George Lucas’ flick needs to show better legs this time around. A 35-40 percent drop would result in another $28-31 million for the prequel-sequel.

Will that be enough to stave off ”The Sum of All Fears”? Affleck’s thriller, in which the actor takes over the Jack Ryan role played by Harrison Ford in ”Clear and Present Danger” and ”Patriot Games,” arrives with good buzz and a plethora of media attention, stemming from its eerily realistic plot involving a nuclear attack in the United States.

But is that storyline too close for audience comfort right now? It certainly didn’t help Arnold Schwarzenegger’s ”Collateral Damage,” which only managed a $15.1 million debut back in February. Still, ”Sum’s” summer release and younger lead should translate into bigger bucks, meaning an opening in the $26-28 million range, and a probable No. 2 finish.

Meanwhile, ”Spider-Man” will continue its box-office streak, dropping another 35 percent to around $19 million and approaching the all-time top five (No. 5 right now is ”Jurassic Park” with $357 million).

The weekend’s other new entry is the spy spoof ”Undercover Brother,” starring Eddie Griffin, Denise Richards, and Chris Kattan. Anyone who doesn’t want to take on the horror of ”The Sum of All Fears” will find silly respite in this comedy, about Griffin’s attempt to foil a plot to turn all black people white. Perhaps $15 million worth of moviegoers will find that a bit less realistic, and therefore more enticing.

The fifth slot should go to one of last week’s top new releases, ”Insomnia” or ”Spirit: Stallion of the Cimarron.” After premiering with $26 and $23 million, respectively, over the four-day holiday, both should see declines to about $12-13 million this week. That should be enough to give ”Insomnia” director Christopher Nolan (”Memento”) a good night’s sleep.

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