There are various ways to average polls over time, and results can differ depending on the types of polls that are included, the time frame over which polls are averaged and statistical adjustments aimed at correcting for systematic differences between pollsters. Post averages do not include surveys from pollsters that fail to provide details considered mandatory by the American Association for Public Opinion Research (AAPOR). Yet state polls have been less accurate historically — in part because they are conducted less frequently and population benchmarks are less precise — which should temper the confidence in the size of any candidate’s advantage. The way polls miss is unpredictable from election to election. While state polls tended to underestimate Trump in 2016, they overestimated Republican nominee Mitt Romney in 2012, and in 2008, state polls showed little systematic error in either party’s direction, according to an AAPOR task force report.

Source: Washington Post October 16, 2020 19:45 UTC