Taken in the aggregate, preelection polls in the United States pointed to the strong likelihood that Democrat Joe Biden would pick up several states that Hillary Clinton lost in 2016 and, in the process, win a popular and electoral vote majority over Republican President Donald Trump. That indeed came to pass. But the election was much closer than polls suggested in several battleground states (e.g., Wisconsin) and more decisive for Trump elsewhere (e.g., Ohio). Democrats also were disappointed at failing to pick up outright control of the U.S. Senate – though it remains a possibility – and at losing seats in the U.S. House and several state legislatures.
Many who follow public opinion polls are understandably asking how these outcomes could happen, especially after the fairly aggressive steps the polling community took to understand and address problems that surfaced in 2016. We are asking ourselves the same thing. In this post, we’ll take a preliminary shot at answering that question, characterizing the nature and scope of the 2020 polling errors and suggesting some possible causes. We’ll also consider what this year’s errors might mean for issue-focused surveys, though it will be many months before the industry will be able to collect all the data necessary to come to any solid conclusions. CONTINUED
Scott Keeter, Courtney Kennedy & Claudia Deane, Pew Research Center