In the closing days of a campaign, every day is Halloween, because the hobgoblins are all real and they genuinely are trying to scare you.
Campaigns are paranoid places to begin with, so when you add the terrible pressures of the final days, it is little surprise that both candidates and their staffs are so jumpy. First, the campaigns are running out of time, which is their most precious resource. Second, by this point each side is totally consumed with rage at the various despicable maneuvers--both real and imagined--of its opponent. Finally, somebody is ahead and afraid to lose position, and...