They made a mistake not noticing the huge number of undecided. Then they decided to allocate them 50/50 when in some states it ended up 70/30 Trump
They under played the white non college degree demographic.
This is a story of huge volatility
Go forward to 2020
There has never been a more stable race with fewer undecideds. After all who is thinking about Trump still
Nationally Biden +8 It is almost exactly translating into the swing states for example Florida +1-2 Michigan +7 ( he won this last time by 0.2%)
To back this up and this is more important when you look at house race polls and even county level the GOP is being destroyed
If I was a betting man I'd say Trump is over represented in the polls
He will hold Texas by 2 but lose Florida, NC, Arizona,WI, MI PA and I'm going to throw in Ohio and Iowa
Over the last two weeks Biden has on average widened his lead.
To look at one poll is statistical nonsense