which of the following be proper responses on election day?

That's not the relevant question, surely - the point is, what woudl the likely effect be. Here's what a comment writer in today's Guardian had to say about that:

"Travelling in the US recently, I asked most Americans I met what they thought the effect on the election of an October spectacular would be.

"All, whatever their politics, believed that a second 9/11 would buy Bush a landslide second term."

And that is why I would expect Al Qaeda to try just that, because a Bush victory would be what they would surely want to see.