Bernie is having heart problems. Should the electorate hold that, and by extension his age, against him?
Yes and no. Yes, his health, and the health of the other candidates, is clearly a legitimate issue in the campaign. Yes, I would prefer a younger nominee in order to emphasize the contrast with Trump if everything else was equal. But no, all of the first tier Democratic candidates, as well as Trump, are in their seventies, so age in and of itself should not be a factor after the rest of the Democrats have fallen away.
A note to my readers: I will be on vacation until 10/18, so posting will be irregular for the next two weeks.