Politico- How could the polling be so wrong?

by Steven Shepard | November 10, 2016
Harper Polling, a Pennsylvania-based polling firm that has worked for Republican candidates and groups, had the presidential race deadlocked in Pennsylvania.

The signs of a polling disaster were all there, but almost no one besides Donald Trump was paying attention.

There were surveys showing Trump winning, but they were ignored by most news outlets.
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Other small Republican firms also released polls in the final days that pointed to Tuesday’s result. Harper Polling, a Pennsylvania-based polling firm that has worked for Republican candidates and groups, had the presidential race deadlocked in Pennsylvania.
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Harper Polling