Comey letter was 11 days ahead of the election in 2016 and for sure played a part in the outcome.
There is an outlier in the poll, IA-01 district shows +9 Trump, in a D held House District. If that's anywhere near true, Wisconsin and Michigan on election night might be interesting. My guess that part of the data could be bad and maybe it is really Trump +5 in the Statewide.
The pollsters changed up their tactics this time. Even heading into election day there were a lot of "undecided voters" in 2016. Which were really Trump voters hiding. This time most of the polls haven't given the voters an undecided choice. The DM Register poll gave them "Undecided" and "Won't Say". That totaled 7% which my guess is that's the embarrassed Trump supporter. I think there's only two ways the polling data is wrong this time. Trump voters are flat out lying to the pollsters (which I think is very possible) or the sampling is off (which I think is for sure true but maybe only 2-3% towards Ds which still puts Biden as a comfortable winner).