None
(Heller is the most vulnerable--I voted for him, followed by Donnelly, and then Heitkamp. Manchin's crossover appeal allowed him to win comfortably by 61-37 in a state which overwhelmingly went for Romney 62-36 in the SAME YEAR)
Incoherent hackery. I'd much rather be a Republican in a Tilt D Swing State than a Democrat in Post-Bayh Indiana
You are right, though. Tilt D swing state Republicans are, generally, in a
much better position than Dems in crimson red states.
But I'm still convinced that 2018 would be a backlash against the culmination of Reps to power.