This seems very important "It’s also that the late substitution of Kamala Harris for Joe Biden (plus a few other oddities) make it hard to guess whether voters will make up their minds at the same pace they usually do." I'm curious why you prefer not to look at state polls -- like PA or WI?
State polls are just individually less reliable over time, and there are a lot fewer of them so it's harder to get a useful average. Right now 538 has 20 national polls that were out in the field on Aug 25 or later, but only 5 during that range in PA and just 3 in WI, so the chances that the state polls will be thrown off by an outlier are a lot higher.
This seems very important "It’s also that the late substitution of Kamala Harris for Joe Biden (plus a few other oddities) make it hard to guess whether voters will make up their minds at the same pace they usually do." I'm curious why you prefer not to look at state polls -- like PA or WI?
State polls are just individually less reliable over time, and there are a lot fewer of them so it's harder to get a useful average. Right now 538 has 20 national polls that were out in the field on Aug 25 or later, but only 5 during that range in PA and just 3 in WI, so the chances that the state polls will be thrown off by an outlier are a lot higher.