I confess, I'm not *very* worried about organized high-level vote-rigging, simply because it would require a well-run conspiracy, and those seem to be fairly rare. Doing something on that scale without big leaks is hard, although not impossible. And heaven knows, if you think that the voting-machine manufacturers are in the tank for the Republicans, it is easy to come up with conspiracy theories. But given the attention on this topic, I'd say it's unlikely.
None of which silences the tiny nervousness at the back of my mind. The actual tally had better line up pretty well with the exit polls, or all hell is going to break loose on Wednesday...