What's the worst that could happen, at the end of the day, and is that worse than the alternative?
Oh... I think that an open primary essentially requires Biden to voluntarily step down first, and if he does I don't think there's really a lot of damage to expect and they could just say they had no other choice.
I think it's possible, though not likely, he could be convinced to.
I also think currently Trump is more likely to win than not if the nominee is still Biden.
Don't get me wrong... The Dems could definitely be hurt by such a thing. If Biden steps down, I don't see how they could really go for anyone other than Kamala (who would lose to Trump), because of the optics. She's not their best choice, obviously. So there is that. Haha