For those looking at early vote data specifically the Republican versus democratic split here is an interesting article on how that measure performed previously
https://www.natesilver.net/p/the-ear...liably-predict
The answer is it’s not predictive. Most of the article is paywalled but the summary is available.
The other important message around polling to get out in light of Trumps voter fraud campaign is that although this election is very close it also has a very high probability of being a landslide in terms of electoral college because of how many very close states there are and how correlated polling errors are state to state.
https://abcnews.go.com/538/trump-har...y?id=115283593
A normal polling error either way will result in a blowout.