Interestingly, on the age front, Bob Dole faced a similar concern at the age of 73 in 1996. 12 years later, while he may have some health issues at the age of 85, it's obvious that he was viable enough at the time. McCain is far more energetic than Dole was.
It's still not a good look for a politicians shooting for the top job, though, isn't it? Especially if your opponents are young and virile (and yes, I include Hilary in that category ) and you've had a practically senile old fart in office for the past two(?) terms. Isn't Dole proof? Age counted against him mightily, if I remember rightly, and he seemed much more youthful than McCain does at the moment. I also notice that the man is fodder every single night for Letterman and all of the other pisstakers - all of the jokes are about his age.