Election models megathread

[Crumpets]

538 has Democrats favored (albeit very narrowly) to hold the Senate for the first time since the model went online.

[Crumpets]

Can someone explain why the Deluxe and Classic models on 538 apparently see Ryan's win last night as hurting his chances in November, but the Lite model sees it as dramatically increasing his chances? All I can assume is that because it's a midterm, the first two treat him as a "one term" incumbent, who are likely to lose in a midterm that on paper should be better for the opposite party?

[Crumpets]

538 has Democrats' odds of holding the Senate at 63%, which is their lowest number since August 23rd. It's a bit odd because the Classic and Light versions of the model still have their odds higher - 70% and 75% respectively, and the models (I think) are supposed to converge by election day, although the other models also have Democrats' chances decreasing over the last couple of weeks. But I'm not really sure what could be driving the Deluxe model specifically to be so bearish on their chances when I think the only difference it has with the Classic model is experts' ratings and I don't remember any huge shifts in the ratings to Republicans in recent weeks, just maybe a few bad polls which should show up in the other models too.

[Crumpets]

What happens in this timeline?

Nuclear exchange/meteorite impact/Yellowstone eruption the day before election day and only mail-in votes get counted everywhere since all the polling places are irradiated/in a crater/under 10' of ash.