The polls, the polls, the polls.
Was just absolutely nothing learned from 2016?
Yes - which is why reputable pollsters adjusted their population weighting for education.
Speaking of which, quotes from November 6, 2016 from noted verified Twitter user Nate Silver:
"Clinton has a 64 percent chance of winning the Electoral College in our polls-only model and 65 percent in polls-plus, putting her somewhere in the range of being a 2-1 favorite. At the same time, it shouldn’t be hard to see how Clinton could lose. She’s up by about 3 percentage points nationally, and 3-point polling errors happen fairly often, including in the last two federal elections
...There’s also reason to think a polling error is more likely than usual this year, because of the high number of undecided voters. In national polls, Clinton averages about 45 percent of the vote and Trump 42 percent.
... public polls — specifically including the highest-quality public polls — show a tight race in which turnout and late-deciding voters will determine the difference between a clear Clinton win, a narrow Clinton win and Trump finding his way to 270 electoral votes."
So, second lesson, Nate Silver/538 is still pretty good at reading polling data.
I understand why people don't trust polls, but they're still useful tools, especially when taken in aggregate.
Poll