Understanding the 2016 US Presidential Polls: The Importance of Hidden Trump Supporters

Peter K. Enns 1 , Julius Lagodny 1 ,  and Jonathon P. Schuldt 2
  • 1 Department of Government, Cornell University, Ithaca, USA
  • 2 Department of Communication, Cornell University, Ithaca, USA
Peter K. Enns, Julius Lagodny and Jonathon P. Schuldt


Following Donald Trump’s unexpected victory in the 2016 US presidential election, the American Association for Public Opinion Research announced that “the polls clearly got it wrong” and noted that talk of a “crisis in polling” was already emerging. Although the national polls ended up being accurate, surveys just weeks before the election substantially over-stated Clinton’s lead and state polls showed systematic bias in favor of Clinton. Different explanations have been offered for these results, including non-response bias and late deciders. We argue, however, that these explanations cannot fully account for Trump’s underperformance in October surveys. Utilizing data from two national polls that we conducted in October of 2016 (n>2100 total) as well as 14 state-level polls from October, we find consistent evidence for the existence of “hidden” Trump supporters who were included in the surveys but did not openly express their intention to vote for Trump. Most notably, when we account for these hidden Trump supporters in our October survey data, both national and state-level analyses foreshadow Trump’s Election Day support. These results suggest that late-breaking campaign events may have had less influence than previously thought and the findings hold important implications for how scholars, media, and campaigns analyze future election surveys.

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Statistics, Politics, and Policy studies the ways that statistical analysis drives public policy decisions, and publishes significant research on the application of statistical ideas to problems that relate to policy implementation.