Errr......wut?
Would you like to be a Democratic senator whose president just got elected on a promise of providing M4A and then decide to be the one who is going to tell all those voters from your own party that ‘feck you, I know better than you’? Especially given that this isn’t an Obama ‘oh well, let’s water it down then’ case, Sanders is going to hit them and hit them hard if they try and stop him.
Nah, they’ll largely fall on line. The few conservative Dems maybe not, but the rest shouldn’t be a problem.