So, the 'lacking experience' attack not having worked, McCain wants to make the case that Obama has bad judgment.  He lights upon Ayers as a case in point. He makes the case, and makes it again and again.  By not being able to cite other examples of bad judgment and show a pattern -- and the this goes also for the subliminal connection to 'terrorist' -- what McCain has done is use up the effective power of the example.  He did the same thing with "I'm a POW."  Even worse for McCain, people begin to wonder that if Ayers is the only case of bad judgment, then there probably isn't so much to the Ayers case, and Obama must have pretty good judgment after all.

It's hard to say who will be swayed by Powell's endorsement of Obama.  One of possible 'October Surprises' has been a possible terrorist attack, which most people feel would to McCain's advantage because of his military experience.  But I think Powell's endorsement, coming from the best known, highest ranking, and trusted (despite the WMD debacle!) may have immunized Obama against concerns about his ability to respond to a military emergency.