These are only returned ballots by party, not how they voted. That is the way I understand it.
I understand that.
I was thinking more about the fact that there seems to be certain key counties around the nation that are supposed to be important predictors. I see post here about I4 corridor here in Florida being key, etc.
I would think there would be exit polling by someone of the people coming out after early voting in these key locations.
While I understand it would be a small sample, all polling, even exit polling on election night is based on small samples.