If Ds win the Senate in 2018, probability it was due to an "out of class" flip?

[Figueira]

As in, Cory Gardner or Marco Rubio suddenly resigning out of nowhere? I guess that's a possibility. I'll go with 60% since, while I think it's POSSIBLE that Democrats will get one of UT/TX/NE/MS/WY/TN, it's unlikely that Democrats will do that while still retaining all current seats and picking up NV and AZ.

[Figueira]

As in, Cory Gardner or Marco Rubio suddenly resigning out of nowhere? I guess that's a possibility. I'll go with 60% since, while I think it's POSSIBLE that Democrats will get one of UT/TX/NE/MS/WY/TN, it's unlikely that Democrats will do that while still retaining all current seats and picking up NV and AZ.

Not to be too morbid about it, but I think John McCain or Chuck Grassley dying suddenly is the more probable outcome.

Also, I could definitely see Collins flipping in a 50/50 Senate if she's fed up enough with Trump.

McCain and Grassley's seats wouldn't exactly be Safe D though, especially with Branstad and Ducey choosing the interim replacements (and Arizona Governors are required to pick someone of the same party as the previous Senator anyway). I guess they'd be more likely pickups than Texas, but that's on the off chance that the opportunity even arises. McCain has good genes; I think he'll survive. Not sure about Grassley.

[Figueira]

The only shot is if Collins runs for Governor in 2018 which - while not impossible - seems unlikely.

she'd have to win, and then she'd probably appoint a GOP Placeholder

If Collins ran for Governor she'd be virtually guaranteed to win, and I'm not sure I need the word "virtually."

And yeah, there would be a Republican appointed to the Senate, so it wouldn't change things in 2018. In 2020 though, that person would be the most vulnerable Republican along with Gardner.

[Figueira]

In either NC or LA, both the Senators died in a plane crash, and the Democratic governor appointed 2 Democrats. And if LA, the special election hasn't been held yet.

The plane crash would have to occur very close to the election, or after it.