The obvious answer is Leonardo DiCaprio -- not because he's particularly well-suited to the role, but because he's Scorsese's muse and good-luck charm, having appeared in the director's last four films (including Shutter Island, due out this fall). But Nikki Finke at Deadline Hollywood Daily, citing her usual no-named sources, says the studio wants a different superstar: Johnny Depp.
My gut reaction to this is that it's typical studio knee-jerk casting: "Let's get the most famous, most popular actor in Hollywood! He's perfect for the part because he's the most famous and the most popular!" But I concede Depp looks enough like a young Sinatra that it wouldn't be completely ridiculous, and obviously he's a good actor. So maybe it could work. (That picture is him in Public Enemies. The hat and old-school suit definitely helps his Sinatraness.)
Depp can sing, as we learned in Sweeney Todd, though Finke says that doesn't matter, as Sinatra's own recordings will be used in the film. But that doesn't mean there won't be, say, scenes set in rehearsals, or other non-performance settings, where the actor (or a voice double) would need to sing a bit. Then again, singing is one thing -- singing like Frank Sinatra is something else. Can Depp do it? Can anyone do it?
For more, Moviefone has picked 10 actors as potential candidates for the role. Vote for your favorite right over here.
Some commenters yesterday suggested Harry Connick Jr., who looks a bit like Sinatra and has the voice down. He's not a bad actor, either, though I don't know about carrying an entire film. He certainly doesn't have the star power of a Depp (or even a DiCaprio), either, which is presumably what Universal wants.
What do you think? Could Johnny Depp do it? Or would it look like stunt casting? Who -- or whom, even -- would you cast?