Why Kerry speaks so incomprehensibly ...

According to Stanley Fish. It's not that he's complex and nuanced:

If you can't explain an idea or a policy plainly in one or two sentences, it's not yours; and if it's not yours, no one you speak to will be persuaded of it, or even know what it is, or (and this is the real point) know what you are. Words are not just the cosmetic clothing of some underlying integrity; they are the operational vehicles of that integrity, the visible manifestation of the character to which others respond. And if the words you use fall apart, ring hollow, trail off and sound as if they came from nowhere or anywhere (these are the same thing), the suspicion will grow that what they lack is what you lack, and no one will follow you.

This implies a deep connection between our language ability and our emotional makeup that gives rise to an amazing practical wisdom in the human animal. If the candidates' speech inherently reveals who is speaking the truth and has a sound moral core, instead of worrying that people vote their feelings and fail to devote enough effort to amassing information and reasoning logically, we should renew our faith in democracy.

UPDATE: Eroding my faith in democracy, John emails "I take it [Fish] thinks that Aristotle and Kant weren't expressing their own ideas."