By the time 2018 comes around, things could be different. Republicans may have the White House
As my HS physics teacher always said: Keep Drrrrrreaming!
I will be too, but I don't expect it.
Who would be though?
Feinstein: Too much of an institution in CA politics plus the top 2 jungle despite her authoritarian streak.
Nelson: Bench too weak
Donnelly: Nah, Dems will be happy to have him
McCaskill: Maybe?
Heitkamp: They'll be happy to have her
Tester: Schweitzer could look at this but more likely in retirement than to challenge
Casey: Too big a name in PA
Manchin: May be governor and no one else can win
So McCaskill and maybe Tester. I highly doubt the Democrats will have very much infighting. There's less ideological purity since the far left is just so out of the American mainstream while the far right is almost a part of the American mainstream ideologies. Plus the Republicans seem to have far more factions. The Democrats have a lot of conflicting points of debate as well, but they are relatively insignificant aside from the NSA (and maybe union vs. environment) and never get brought up because people don't think much about them.