Let's not kid ourselves - this race was over six months ago when The Dark Knight was released.
Heath Ledger will become the second-ever posthumous winner of an acting Oscar (Peter Finch was the first - he won for Network in 1976). And he won't win just because he's dead. He will win because he accomplished one of the most jaw-droppingly fearless performances of the last ten years (at least). He'll win because every brief moment he has on screen is audacious and mesmerizing. The applause during the ceremony's "In Memoriam" montage will honor his life, but the Oscar will honor his performance.
There is a chance, though, that the Academy will decide to hand the award to someone who can actually be there to accept it. If that's the case, it will probably go to Philip Seymour Hoffman, making him the 13th person to receive Oscars in both acting categories. His role in Doubt has been deemed a leading role by everyone except the Academy, so placing him in the Supporting category gives him a boost. Michael Shannon (Revolutionary Road) and Robert Downey Jr. (Tropic Thunder) gave standout performances, but they're still classically supporting roles and Josh Brolin (Milk) simply gets lost in a sea of great performances.