Interesting observation in this reply to Nate’s tweet:

So in elections where there was an incumbent running for re-election (or, technically, in the case of Ford, election) the polls held out. If the incumbent was ahead, they won, if the challenger was ahead, they won. The misses came in open seat elections.

— Mike (@Rn_for_Fn) September 8, 2020

That actually makes a lot of sense, since an open-seat election can’t, by definition, be a direct referendum on the incumbent (which means it’s more likely to have a large pool of undecideds who in turn are more susceptible to last-minute developments, October surprises, etc).