The Sound Guy
Pursuit Driver
A couple of the pollsters I watched mentioned it several times; they really don't know why this happens, but they acknowledged that it's real.
I dunno why they can't understand it, I think it's simple.
A good sized group of Trump voters are conservatives who:
Don't trust the Govt
Don't trust the Media
Don't trust pollsters in general.
Don't believe it's anyone else's business who I'm gonna vote for
and
Just want to be left alone dang it!
<Note: I identify as the above>
They ignore the poll calls whereas your typical Liberal can't wait to tell them what they think and who they are voting for.
If they manage to get ahold of someone who likes to answer polls and claims to be GOP, it's likely a RINO or an never-Trumper, who claims to be voting for the other person or 3rd Party.
Thus there is a good sized group that will NEVER show up in a poll, may often not even vote, but feel Trump *is* anti-establishment and someone they feel can support to make it worth voting, so he has a large set of "Stealth" voters that show up and throw the polls off.