When Bruce Springsteen recently announced that he’d be campaigning for President Obama in Ohio and Iowa this week, and when he officially endorsed the president yesterday with a letter posted on his website, no one was surprised. You would have to be dense not to pick up the progressive vibrations in nearly four decades of Springsteen’s music, and he’s actively promoted the Democratic nominee now in the last three elections.

It’s unclear if celebrities have any political influence on voters, but if they do, it seems to diminish exponentially with repeated exposure. Take George Clooney, for example. He’s the most famous celebrity political insider, but because he’s so involved, his actual endorsement means much less to average Americans — it’s simply taken for granted that he would support Obama again.

That’s why the Republicans thought they had an ace in the hole with Clint Eastwood at the Republican National Convention. Sure, Eastwood was a famous conservative, but he had rarely if ever been willing to lend his celebrity to a national candidate. When viewers saw him take the stage, it had the potential to make an impact that would dwarf the combined wattage of Clooney/Springsteen/Oprah. Alas, it didn’t exactly work out that way.

But what celebrity has that kind of clout these days? Who are the famous Americans that both political parties would welcome to their fold? The Sean Penns and Kid Rocks have already made their bets and spent their capital. Who might still be able to move the needle? You know, besides Lindsay Lohan and Honey Boo Boo.

Tim Tebow. A conservative Christian, he’s spoken up on issues that are at the core of the Republican social platform. But the New York Jets quarterback has not campaigned for either candidate, preferring to remain on the sideline. Pun intended, Jets fans.

Robert Pattinson. No, he’s not an American citizen, but no matter. A cuckolded Team Edward still carries a lot of weight, especially during an election season where the women’s vote is so crucial.

Daniel Day-Lewis. If a candidate can get the Oscar-winning actor to dress up as Lincoln on stage, I think they can assure victory.

Bill Murray. Don’t think for a second that both camps haven’t been calling Murray’s infamous 1-800 number non-stop for weeks. Landing him would be more than just a Cinderella story. Maybe they should schedule random kickball games

Jeff Bridges. Not only is he the Dude and a movie president (The Contender), but he’s the soothing voice of Duracell batteries. You like Bridges, your grandmom likes Bridges, isolated North Koreans like Bridges.

Ed Harris. He portrayed John Glenn in The Right Stuff and John McCain in HBO’s Game Change, and he wears a sunny American optimism and gravitas that candidates envy.

Who have I ignored? Is there a revered celebrity whose endorsement might actually get your attention. (Here’s two lists of peoples who have already committed, either for Obama or Romney, for you to peruse.)