It depends on the reasoning. For example, they might say to themselves, there is all this ignorant intolerance of Mormons out there. If a Mormon were to be elected president, probably a lot of that would disappear. I'm sure many Catholics thought something similar about Kennedy.
Is there some kind of mantra, JFK=Mitt Romney that we aren't all aware of? I missed class that day, I guess.
Trying to equate the two is a red herring, IMO. AND, you're missing the most important thing...JFK was a dem. We're talking about the Republican nomination with Mitt, and if he gets the nod, Republicans will be shut out of the WH and the dems will gain a large majority in the congress...don't think they aren't counting on it.