A look inside Hollywood and the movies. : THE POLITICAL DEPT. : Die Hard 3: Bruce Willis Saves the White House From (<i> fill in the blank</i> )

Wonder how Bruce Willis ended up at the Republican National Convention, joining a host of other action-adventure heroes such as Chuck Norris and Arnold Schwarzenegger in the camp of President Bush?

The scenario begins in mid-August on the Pittsburgh set of Columbia Pictures’ “Three Rivers,” a summer 1993 release directed by Rowdy Herrington (“Gladiator” and “Road House”). Willis, who stars with Sarah Jessica Parker as a couple of river patrol cops, puts through a call to the White House and asks to speak to Bush. The name rings a bell. The President gets on. After brief introductions and some pleasant chit-chat, the superstar is invited down to Washington for a visit.

Willis secures a private plane and heads for the nation’s capital. Observing the chief of state in action for five hours, he volunteers to show up in Houston the following week, where he was seen sitting in a box with First Lady Barbara Bush.

It’s a departure, on the face of it, for someone who doesn’t wear his politics on his sleeve.

“Bruce is registered as an independent, but wholeheartedly supports President Bush’s campaign,” acknowledges a Willis insider. “After educating himself in both arenas, he’s chosen his path of support.”

Willis refuses to comment on his upcoming involvement or on speculation that he, like others in his income bracket, may be factoring his pocketbook into his politics. It’s a good bet, however, that he’ll surface on the campaign trail again after “Three Rivers” wraps in early September.

“I wouldn’t be surprised to see Bruce out there,” says one source close to him. “The convention is probably not a one-shot deal.”