In the wake of Donald Trump’s surprising victory in the 2016 U.S. Presidential Election, there’s been a lot of discussion in the news about what might have gone wrong this year with public opinion polling, which clearly did not foresee this outcome.
Most polls showed Democratic nominee Hillary Clinton holding onto a slim but steady lead for most of the election cycle. During the week prior to the election, the Real Clear Politics polling average showed Clinton with roughly a 3 point lead in the national polls. Furthermore, on the morning of the election, most major forecasting sites pegged Clinton’s chances of winning at 85% or higher (My forecast and that of FiveThirtyEight were two exceptions. We each gave Trump slightly better chances, at around 25-30%).
But a Clinton victory was not to be. For whatever reason (and we will likely not have a definitive and satisfying answer to this for months), polls underestimated Trump’s support in several key regions of the country. Specifically, Clinton lost in Pennsylvania, Michigan, and Wisconsin, despite the fact that polling averages showed her up in these states by 1.9 points, 3.4 points, and 6.5 points, respectively. Clinton does seem poised to win the popular vote, if that’s any consolation to her supporters. But she’ll become the 5th presidential candidate in history to lose the Electoral College despite winning the popular vote.