AP thinks it is because there has been a massive uptick in support for a Mormon candidate. I think this is really how people think.
See, I work in a law office in Trial Support. I go into the courtroom and sit in front of the jury doing my job. I also, at one time, had long hair. And I would often hear the same thing before a trial. “Maybe you should cut your hair? I don’t have a problem with it, but the people on the jury might.” And you know what? I think the people who suggested it did have a problem with it — but they also knew that they shouldn’t have a problem with it, so they make an effort to get past it. I think this is an admirable trait, and I think that most Americans are like that. They have an irrational issue with something, but they know it is irrational and move past it. The problem is, they assume that there are other people out there who don’t move past it.
So yeah, I have no problem believing that 80% of America says they don’t have a problem with Mormons, but 45% think that other people do. Because 35% of the population has a little problem with Mormons, but they are going to look past it.