The third and final Presidential debate between Barack Obama and John McCain took place one year ago last week—Oct. 15, 2008. It's worth recalling that encounter now for its remarkable revelations of things to come.   The debate was marked by heated charges from McCain and cool responses from Obama—what The New York Times the next day called his "unflappable demeanor."        Running out of time and depleted of character, McCain strained in the debate to disqualify his young rival with attacks on Obama's character. The highlight, or lowlight, of this exercise was the Republican nominee's decision to mimic his hapless running mate by tying Obama to "a washed-up old terrorist" named William Ayers. Four decades before, Ayers had been a member of the violent Weather...