They won't. The purpose is not to overturn the election, although they'd take that of course regardless of legitimacy, but rather to discredit and weaken President Bush. It won't work.
Oh, it's worse. DUers and the LL are convinced that there's massive voter fraud to be unearthed! It's not done until 2008, just like 2000 wasn't done until 2004 (or, no, wait, it's like a CD: they're justing rolling it over). Exit polls are infallible, don't ya know? (Except, well, in New Hampshire.)
And if no fraud is found, well, it just means the ballots were altered ... and the poll books ... etc., etc. I tell you, it's a religion. Geesh.