Most likely folks are hiding their decision to support Trump because they do not want to called all kinds of names.
I posted this in another thread, but I will repeat it here. Over the weekend, I was with extended family, all of whom are relatively conservative. Several family members said they were turned off by Trump’s statements about the judge and other comments, but that they agreed with him on policy. In my opinion, a lot of the undecided vote is in this camp.
Trump needs to lay off the schtick through November. The good news is that these voters are there to get, and I suspect a number of them will come around when the election is looming. But right now there are a lot of right-leaners who are not on board yet.