Trump won in 2016 by keeping the Republican coalition together and bringing in 2,000,000 new voters who wouldn't have passed the Likely Voter polling screens.  Trump won by ~80,000 votes in just the right places.

Trump has fractured the Republican coalition.  White suburban women left to vote for the Democrats in 2018 and there's no indication they are returning.

While it is possible he could bring in 2,000,000 new voters it is equally likely Biden will bring in 2,000,000 new voters as well.  The latter is much more likely than the former.

It is hard to keep in mind polling is descriptive of the time the polling took place not predictive of the future.  When asymmetrical shocks, like 2,000,000 unexpected voters showing up, happen things get a wee bit weird.  And, in fact, the national polling was fairly accurate.  Clinton when in with about a 2 percent lead and she won the popular voter by around 2 percent.  She didn't win because the US has an archaic election system designed for slave owners and when the horse was the fastest land transportation.


She believed in nothing; only her skepticism kept her from being an atheist. -- Jean-Paul Sartre