State-level presidential polls—especially in the swing states—were
badly and systematically wrong, by amounts not seen in decades. The polling averages indicated that Clinton would win
Florida and
North Carolina by 2 percentage points,
Pennsylvania and
Wisconsin by 5 percentage points, and
Michigan by 7 percentage points. Instead, Trump won all five, for a total haul of 90 electoral votes. The state polls were so inaccurate that Trump almost won
New Hampshire, where he’d been trailing by 5, and
Minnesota, where he’d trailed by 9. Across all states, on average, Trump’s margin of victory was 5 percentage points greater than our
polling aggregates expected it to be.
Given this data, no reasonable poll-based presidential forecasting model could have predicted a Trump victory. There was no interpretation of the available public polling data that supported that conclusion. This was not a case of confirmation bias or analysts reading into the data conclusions that they wanted to see. The evidence supporting a Trump victory
did not exist.