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

Understanding the 2016 US Presidential Polls: The Importance of Hidden Trump Supporters. Peter Enns, Julius Lagodny and Jonathon Schuldt. Statistics, Politics and Policy, https://doi.org/10.1515/spp-2017-0003

Abstract: 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.

Check also: Social Desirability Bias and Polling Errors in the 2016 Presidential Election. Andy Brownback and Aaron Novotny. University of Arkansas Working Paper, July 2017, http://www.bipartisanalliance.com/2017/08/social-desirability-bias-and-polling.html