I think it’s hard to say, he needs to do well 3/15 to avoid being “mathematically squeezed” into impossibility. I think North Carolina/Ohio should receive the lion’s share of his attention, but he needs to get better at realizing every campaign counts. Doubly so for his legion of young reddit supporters who focused insanely on Michigan.
Not saying it was dumb to care about Michigan, but if he had done 10% better in Mississippi that would’ve been almost as important delegate wise.
So while I think NC/Ohio should be where he puts all his effort, make sure he’s at least contesting in Florida and Illinois.
In terms of allocating limited resources I’d hit NC/Ohio hard, equally (relative to their size) and then Illinois prioritized a little less. Florida still work to get awareness and do more than he did in places like Mississippi–really in a long proportional delegate race there should be no state you just “concede.” These aren’t FPTP WTA contests, conceding a state makes no sense, ever. But Florida should attract less money/time than the other three because it’s likely his efforts will be the least rewarded there since Florida has a closed primary and you have to switch something like 23 days ago (29 before the primary), and given Bernie’s large number of young and independent voters the likelihood enough of them have bothered to pre-update their registration means this is a state where late gains are probably going to be less likely/muted.