Age: 62
Occupation: Governor of California
Previous TIME 100 Appearances: 2
The former Mr. Universe took on California and made it clear he wouldn't be strong-armed by his own party on issues like global warming. Term limits bar the Republican governator from re-election this year, though his approval ratings — at a record low in March, as his state continues to be plagued by fiscal woes — might have served the same purpose. Still, as the leader of the union's most populous state, he's a force to be reckoned with.