ok. then, as sd asked, identify your tipping point.
1. If it is Biden that is clearly going to win, 100% as protest vote
2. If it is Biden and he is Clinton 2016ing it up (likely winner but keeps rough ridin' up his own coronation) and there are like 4 others lurking/waiting for him to do something even dumber than the other million dumb things he did just yesterday, almost certainly still Bernie assuming he isn't like 5th
3. If it is Biden vs. Warren as the only hope 100% Warren
4. If Kamala comes out more stongly for Medicare for All and some of Bernie's other policies and Warren is still kind of waffling on Medicare for All, then maybe Kamala.
I kind of wonder if Bernie would endorse Warren if she overtakes him and he is 0-3 on early states. But I think that is unlikely given polling in NH.