I don't expect things to come down to such thin margins... if the conventional wisdom of breaking independent voters is correct then we should end up a little ways away from the tie we have now.
But, if we do have a close election that comes down to legal battles and recounts, all hell will break loose... protests, riots, and vigilantism. Mix in a major terrorist attack, and we could be looking at a wrecked republic.
Nader is not the issue.
If the vote differences are hundreds in one of these places where the Republicans tried one or another of their dirty tricks (tearing up voter registrations, bs about registrations not being on the right weight of paper, jamming phone banks, stories about voting leading to government agencies investigating you, Diebold machines without a paper trail etc), can anyone honestly say the violence is not justifiable?
The whole reason we say violence is unacceptable is that the system provides an alternative to violence that let's everyone be heard. When the system no longer provides that alternative, when certain voices clearly are not allowed to be heard, people have two choices of response --- suck it up, or violence. Didn't our fearless leader just tell us that sucking it up, appeasement, was for pussies?
This is why I'm pro-gun: always preserve the possibility of an armed uprising. I know I might sound like a nut when I say that, but it's true.
I suspect that shooting Ralph Nader right before the election would double or triple his vote.