I feel like Clinton winning NV and getting SC by a huge (20+) margin shifts the narrative to a question if Sanders can win outside of his best states. That makes Super Tuesday do or die for him.
I don't think she's going to win it by 20. The races naturally tighten over time, and Sanders will pick up more black voters as they learn more about him. I guess the real calculation is what she has to win by (and not a melkr_ style "if she doesn't win by 400 then really it's a bernie win"). Is 15 enough? I'm not sure. You kind of have to do a second order calculation to figure out what this means for minority voters nationally.
edit: I also think the marginal benefit of endorsements for Sanders is tremendously more positive than for Hillary. She has hundreds and they are sort of taken as given and are not focused on by the media. The remaining endorsements will get a lot of attention (and could be from influential endorsers).