Mr. Obama’s probability of winning the Electoral College advanced to 83.9 percent in the Nov. 6 forecast, up from 81.9 percent on Wednesday.
Causation? The long answer, in Silver's words: "[A] secretly recorded videotape ... released on Sept. 17 showing Mitt Romney making unflattering comments about the '47 percent' of Americans who he said had become dependent on government benefits."
The short answer, in blunt reality: Mitt Romney.
Silver recalls that he issued a tweet advisory after the tape's release, warning that "Ninety percent of 'game-changing' gaffes are less important in retrospect than they seem in the moment." This Fizzle Effect is infuriatingly real for devout partisans who always hear in the opposition's latest blunder the explosive beginning of the dramatic end, only to watch the polls flatline.
Politics fans (as in fanatics) are much like the old Kremlinologists, examining every major player's gestures, words, syllables and inflections for decisive omens of shifting power relationships. Meanwhile the inattentively average citizen sighs, "Huh? Oh yeah that guy's running for some office, isn't he?"
Leave it to Mitt Romney to find a way around American apathy.