Along these lines...To piggy back off this a bit....
I am not convinced on this entire argument that Bernie just needs to win Iowa and NH to prove he's capable of winning and, therefore, electable. The man literally won states in 2016. Quite a few of them! It's not like straight cis-gendered white men have clouds of doubt around them. The fact that we're even talking about the possibility of not winning NH is...it's kinda indicative of his issues IMO. NH shouldn't even be close. He should be running away with NH. I cannot fathom why a voter in SC is suddenly going to go "Oh wait that Bernie guy who won states in 2016, including NH, can actually win!? I gotta support him now." It just doesn't work for me logically. Obama having to prove he could win? Absolutely, because people are racist shits. Hillary having to prove she can win? Absolutely, because people are sexist fucks. An old white man, who ran before, suddenly having to prove he is capable of winning a state he won by like a bajliion points 4 years ago that will somehow change the makeup of the race? I don't see it.
In the hypothetical that Sanders didn't run again... I could see Warren being the nominee? I'm less convinced vice versa.