One reason the polls were wrong?

A lot of people think that the reason why polls were wrong was because of “shy Trump voters.” You talk to someone, they say they’re undecided, or they say they’re gonna vote for Biden, but it wasn’t real. Then, maybe if you had a focus group, they’d say, “I’m voting for Biden, but I don’t know.” And then your ethnographer could read the uncertainty and decide, “Okay, this isn’t really a firm Biden voter.” That kind of thing is very trendy as an explanation.
But it’s not why the polls were wrong. It just isn’t. People tell the truth when you ask them who they’re voting for. They really do, on average. The reason why the polls are wrong is because the people who were answering these surveys were the wrong people. If you do your ethnographic research, if you try to recruit these focus groups, you’re going to have the same biases. They recruit focus groups by calling people! Survey takers are weird. People in focus groups are even weirder. Qualitative research doesn’t solve the problem of one group of people being really, really excited to share their opinions, while another group isn’t. As long as that bias exists, it’ll percolate down to whatever you do.

Fascinating interview at Vox.