Audacious Epigone graphs where the polls underestimated Trump (red) or Clinton (blue).
He offers a number of explanations for the patterns, including this interesting east-west distinction that first emerged during the Republican primaries:
Another thing that astute commentators noted from the beginning but that the polling agencies never fully picked up on was the nationwide east-west divide. The dynamics in play here are the rootedness, manufacturing, and populism of the east versus the transplanted, service-oriented, libertarianism of the west. Trump did better than expected in the east and worse than expected in the west.As a minor point, that’s why election night was over almost shockingly fast: Trump did well in the East and Central time zones, so there was no need to wait around for, say, Arizona.