I have many friends that live around here that are closet Trump supporters. They don't talk about it to their friends for fear of getting into fights with their friends. Several of them won't talk to the pollsters. I have heard on talk radio of the same thing when callers call in. I also know of several married couple that are at odds with their spouse and have gotten strong argument about this topic.
I wonder how far the polling results are off because people do not want to admit that they support Trump. From the wild swings in the polls there might be something to this. I guess only time will tell.