That bias against responding covers a number of different elements, including geography. One top Democratic strategist who requested anonymity to discuss candidly what went wrong with the 2016 polls pointed to difficulty in reaching voters in more rural districts because of spotty cellphone service.
The same strategist added that many of these voters also may choose not to participate in polls “because they don’t like the establishment and they don’t want to take a survey.”
The yawning education gap among white voters’ preferences — Trump clobbered Clinton among white voters without a college degree, while the two ran neck-and-neck among those with a degree — means that nonresponse bias may have been determinative, said Democratic pollster Nick Gourevitch, a partner at Global Strategy Group. And it may have been going on for some time.
“I think it’s very plausible that for years pollsters have been over-representing educated voters, and that it only came back to bite us recently because it was a key driver in vote preferences this time,” Gourevitch said.