Nate Cohn with another dive into polling issue in the Times. An interesting outcome he is seeing is that there is a split between web polling and phone polling and it tracks the age of the voter. Obviously pollsters don't like web polling because the sample self-selects, but ignoring the actual outcomes, Cohn says that in web polling he doesn't see any of the supposed drop of in Biden's support among <30-35 voters, that is only showing up in phone polls.
I think it's just another bit of evidence that beginning with Millennials, phone polling now probably generates just as self-selected a sample as a web poll because the young generations do not have the same predisposition to answer their phone just because it rings that much of the older generations are still conditioned with.
No longer being able to get a reasonably unbiased sample by just ringing phones at random is the 700 gorilla in the corner for the future of political polling.