> It was both the sample (read actual reports from pollsters on how hard it is to get a sample these days... people DO NOT want to participate in polls) and an underestimate of the number of voters the Republicans would get to the polls.

Exactly, polling is very difficult, and getting even more so.

I was polled a few years ago by Gallup or Pew (or one of the other well known ones). The call was from an unknown number and I took it. No way I'd do that now with all the robocalls.