The movies best chance to haul in an Oscar Nomination perhaps lies in the hands of Heath Ledger. It's a courageous, bold choice of casting, definately a risk for Ledger with something he's never played before, if written well and performed well Ledger will have an oppurtunity to steal the movie as well as perhaps deliever a psychologically intense character. The ACADEMY seems to always love rewarding actors doing things outside their norm and with make-up, (Cate Blanchette, Jamie Foxx, George Clooney, Nicole Kidman, Charliez Theron some recent ones come to mind). Screen time won't really matter if Ledger/Joker isn't in it too much. Anthony Hopkins, Geoffrey Rush, and To me, anyways, it always appears that the Academy love to honor Actors with the award for a previous movie they were in, not the movie they actually won if for. Russell Crowe got it for Gladiator, but acutally won it with The Insider, and Denzel Washington won it for Training Day, yet most likely won it for The Hurricane.
So put me down for Heath Ledger being the best chance at a nomination!