Why Did the Polls Get So Much Wrong Again in 2020 US Election?

Welcome to Light On Light Through, Episode 158, in which I discuss why the polls got so much wrong, again, in the 2020 US Presidential election.  They did predict that Biden would win, which he did, but by smaller margins in several states than projected in the polls.  And he lost Florida and Ohio, which the polls said he would win.  Why did this happen, again (it happened in 2016), what can be done about it, and what are the implications of this failure in polling for the future?

Further reading:  "A Black Eye: Why Political Polling Missed the Mark. Again."  The New York Times