Just a quick note. When Clinton came out of the conventions with a solid polling lead, I started writing that she would likely win, unless we saw an "October surprise," such as an economic downturn or a terrorist attack. Ironically, a couple of weeks ago, and right before the pneumonia/fainting mess, our campus magazine interviewed me on predictions, and I gave the same spiel.
Now, we can add to the pneumonia/fainting incident, the bombs in New York, one of which went off, another mall attack, and who knows what comes next?
This isn't 9/11, nor the 2008 financial panic. Not even close. But, a bunch of small stuff can collectively have the effect of a big event, and remember that the default when one party has won two elections in a row is for control of the White House to flip. The state of the race is uncertain.