Looks like it's up to 80 now, at least as I'm looking at it. No jaw-dropping new polls since yesterday - maybe now that the first debate is over and there wasn't a clear Trump win they have uncertainty going down?
Nate said when they launched the model that if they told the model the election was that day, Biden's odds would be above 90%. So if Biden's numbers stay even, we should expect to see his odds increase as we get closer to Election Day.
Anyway, I made a simple swing/trend map from 2016 for the current forecast (at least, current as of a few minutes ago). Red is a Democratic swing and trend, gray is Democratic swing but Republican trend, and blue is Republican swing and trend. If this is accurate, then Biden's popular vote advantage is mostly coming from Republican states, not Democratic states. It's probably not very accurate, but it does make some sense given polls showing Biden doing reasonably well in rural areas.
Edit: fixed Vermont.
More likely to be a problem with polling areas on the political extremes. At a certain point, you are statistically much likelier to have errors in favor of the minority position than in favor of the majority position. This shows up when polling demographic groups (Republicans always overpoll with black voters), but is also an issue when polling places like Wyoming (Democrats overpoll) or California (Republicans overpoll), at least as long as their actual results are very lopsided.
It’s not usually probed much because we mostly care about polling in close races.
