At 76, plainly this could be a factor. Yet, it could also be an asset. Towards the end of your life, do you become more or less concerned with appearances and your reputation? The fact that he is in his twilight years could well be argued to increase his claim that he will do what no American President has done to any significant extent in this century–at least since Harding: dramatically decrease the size AND POWER of the Federal Government.
I will add, too, that with regard to the newsletter issue, the best policy is to deny, deny, deny. We all know the game that is being played, and you can only win it with evasion and dishonesty. It was the Clinton policy, and if he were running, Clinton would easily be reelected today. Even if confronted with video to the contrary, he needs to deny, deny, deny, then focus on the fact that he is not and never has been a racist, but that our current President plainly has, speaking in his own book in a derogatory way about his maternal grandmother as a “typical white woman”, spending his time hanging around radicals, and in particular spending hours weekly with the demonically racist and hateful Jeremiah Wright.