Undecideds are breaking now for Trump....everyone who was ever for him hasn’t left him. Contrast that to Clinton. She’s got a few die hard supporters but given a choice between exciting unique Trump and same ol’ crabby Clinton most for her are either going to vote trump or stay home.
The ridicule in the wake of the "basket of deplorables" and the large number of people signing up to call themselves deplorable, has helped let people know it's ok to stand up and be counted. I doubt there are many folks who lie and say they will vote for Trump when they won't. But there are a lot who will say they are voting for Hillary when they won't. It's an act of bravery to suggest even that you are undecided.