Where there's a Willis there's a way -- and it could be back into Demi Moore's heart.

That seems to be the case in recent weeks as action star Bruce Willis is seen more and more at the side of his sexy ex-wife. 

The latest sighting was Sunday afternoon in Santa Monica, Calif., as a relaxed-looking Demi and Bruce lunched with their three daughters -- Scout, Tallulah and Rumer -- and Bruce's mom at the exclusive Ivy on the Shore restaurant. 

Afterward, they strolled along the city's famed Third Street Promenade for a leisurely shopping expedition. 

The one-time power couple, whose bust-up in 1998 stunned Hollywood, looked like an old married couple as they made small talk, smiled and laughed. 

On July 23, Bruce and Demi popped up together at the White House. 

They joined President Bush in encouraging Americans to adopt kids in foster care and had a long, friendly chat afterward. 

And on July 4, the Die Hard actor and his leggy ex were spotted in Hailey, Idaho, where they happily watched a holiday parade together. 

During the festivities, Demi placed her right arm around Bruce's neck and gave him a tender and lasting hug. 

So, what gives? 

When the couple split, they blamed their breakup at least partly on conflicting film schedules that kept them apart for months at a time. 

But Demi's career has nose-dived. Once commanding more than $10 million per picture, she reportedly took a huge salary cut to appear in the upcoming Charlie's Angels sequel. 

Bruce, still at the top of his game, has eased his grueling workload a bit. 

And while he's enjoyed an endless parade of beauties in the past four years, observers say none has generated the passion Bruce had with Demi, who now also finds herself very much single after a recent split with longtime beau and personal martial-arts instructor Oliver Whitcomb. 

Pals of the couple insist the pair remain friendly and enjoy regular outings with the kids. 

But nobody is willing to say -- at least publicly -- whether all this togetherness could lead to something more.

For more news, entertainment and sports coverage, click here for NYPost.com.