All of them.
Nelson was lazy, McCaskill and Donnelly sold out their base like cowards, and Heitkamp got into some issues around the Kavanaugh hearings.
Heitkamp sacrificed her entire political career to do what was right regarding Kavanaugh.
More accurately, she did what was right because she knew she had nothing to lose by that point.
Actually, she was considered the slight, but clear favorite to win reelection before that vote, few people had her worse than tilt D. It may be that an upset was gonna happen anyway, but - despite what some on Atlas like to pretend - hindsight is 20-20.
Heitkamp would've lost either way, how many people actually know their senators, not to mention how they voted on Kavanaugh. ND is just too red of a state for Dems to keep winning in, and Heitkamp wasn't tied in with state politics like Manchin. I feel like we're giving voters too much credit by assuming they know how Heitkamp voted on Kavanaugh, and the vote deffinately didn't sway ND senate in 2018