WSJ: “Polling averages suggest that, in the popular vote, Mr. Biden is now running 4 percentage points further ahead of Mr. Trump than Hillary Clinton ultimately did in 2016. If early election-night reports show that Mr. Biden has performed 4 percentage points better than Mrs. Clinton in states that can report their ballots quickly—such as Florida, which she lost by 1.2 points—Mr. Trump will almost certainly lose. Even if Mr. Trump held a narrow lead in Michigan and Pennsylvania based on counts of predominantly in-person ballots, his hopes of recapturing those states would have to be tempered by the likelihood that late-counted mail ballots would pull both states in the direction of the four-point shift observed in states that had nearly completed their count.”
“A similar analysis can be applied to fast-reporting counties within slow-reporting states. Mr. Trump won Berks County, Pa., by 10 points in 2016, boosted by rural white voters. If we know on Election Night that Mr. Trump is winning Berks County by just 5 percentage points, it will be strong evidence that Mr. Biden is on the way to winning Pennsylvania back for the Democrats.”