One important election night twist: early mail ballots are really good for Biden in Arizona so far, reversing the traditional pattern (you may recall McSally led and then Sinema over took post election day).
Now, I'd expect Biden to have the Election Night lead in Arizona.

This could change as more mail ballots come in, of course. But if this holds up, it would complicate the kind of doomsday scenario we've talked about, where Trump led on Election Night and Biden overtook later. At least here, it could be reversed.

Yes, but Arizona is unique: it's the only battleground that counts mail votes first *and* won't have a full count done by the end of the night. In this respect, it's the flip side of PA. FL/NC ought to have pretty decent counts at the end of the night. https://twitter.com/mravitch/status/1319970557039906817?s=20

So in a very close election, we'll know FL/NC have gone for Trump (or know they're extremely close), but we probably won't have a decision in either PA/AZ, with Biden up in AZ, Trump up in PA, and each side having cause to hope they'll flip the result in the late count

Yeah but the potential magnitude of what we're talking about in AZ/PA is fundamentally different https://twitter.com/jdrouskirsh/status/1319973282540441600?s=20