538 had the Clinton Polls-Plus forecast at >99% with an average polling lead of 21 points.

[paulthompson]

9. No early voting

And New York plus four out of five states the next week allow no early voting. That's a big boost to Sanders, since Clinton does very well with early voting. It allows for a late swing.

Let's say Sanders does well at Thursday's debate. In a state like Florida, by the time the debate in Miami happened, 80% had voted already, so his performance didn't matter much. In New York, it'll be close to 0% voted already (there's a small number of absentee voters). Oh, and Sanders lost early voters in Florida by about 35 points, but lost election day votes by about 12 points. In state after state, he gets a late swing in his direction. That will be amplified with no early voting.