There is a great deal of speculation but no clear answers as to the cause of the disconnect, but there is one point of agreement: Across the board, polls underestimated Trump's level of support.

We’re making this change to ensure our survey samples properly represent the now roughly half (47%) of U.S. adults who only have a cellphone.

Telephone surveys face numerous challenges, but some positive developments have emerged, principally with respect to sampling.

With 89% of U.S. adults online, survey research is rapidly moving to the Web. But 89% is not 100%, and surveys that include only those who use the internet run the risk of producing biased results.

No research has compared app-based surveys with polls administered via Web browsers. Our new, experimental work compares the results of these two modes.

An estimated 46.5% of U.S. adults are cell-only today. To keep pace with this trend, the Pew Research Center will increase the percentage of respondents interviewed on cellphones in its typical national telephone surveys to 65%.