The last few national elections have seen a mostly unreported trend in initial exit polling. They are almost invariably underestimating Republican voting percentages.
This is because there is a small but significant chunk of the right that has dropped out of what one could call the mainstream conversation. Their world is Fox and Breitbart, and anyone doing an exit poll is part of the liberal MSM.
I am guessing that this is also the case in phone polling. If one lives amongst these conservative communities one notices that the degree of alienation is quite profound. Their world is slipping away, or what they imagine was their world.
This leads me to believe that the election is much, much closer than polls are indicating.