In other words, we need to brace ourselves for a “blue shift” in states like Pennsylvania. That is, states that primarily report Election Day results first could show Republicans with an initial lead on election night only to then shift toward Democrats as more mail ballots are counted. To be clear, this won’t be true everywhere. Some states, like Florida, are already counting early votes and will likely report a lot of its early in-person and mail votes ahead of many Election Day votes.
Right now, our forecast estimates that about 6.8 million votes will be cast in Pennsylvania, on average, and the average popular vote result gives Biden about a 5-point edge over Trump, 52 percent to 47 percent. If that panned out, that means Biden would win about 3.6 million votes to Trump’s 3.2 million (with a few additional votes for other candidates). And if the vote count followed what we saw in the primary, less than half of Biden’s votes would be in by 3 a.m. on election night, whereas around 70 percent of Trump’s would be reported.
That means we could be looking at a situation where Trump has about a 16-point lead, 58 percent to 42 percent, based on approximately 60 percent of the total expected vote. But over the course of the next few days — again, assuming the same pattern we observed in the primary — Biden would win two-thirds of the remaining votes, which would precipitate a 21-point shift in the overall margin from 3 a.m. on election night to the final result, as the chart below shows.
This is going to be fun, and horrifying.