Florida, and there's almost no doubt in my mind about it. He probably would've done slightly better than Clinton in the panhandle, since he would've been able to pick off more populist, "ancestral" Democrats with his economic-centered message and his moderate position on guns. It's where his strength was the strongest in the primary. However, he would do much worse in Southeast Florida - a lot of those affluent retirees and Cubans who would pull the lever for Clinton wouldn't do it for Sanders, and for this reason Sanders's margin in Florida would've probably been worse than Clinton's.
I don't see him doing too badly in North Carolina. It was by far his best former-CSA state primary, the only one where he was able to crack 40%, or even 35% iirc, and he didn't really contest the state at all. Contrary to popular belief, I don't think black turnout would've depressed significantly under Sanders. He has a 73% favorability rating among blacks nationwide, and from anecdotal, personal experience, most black people were fine with voting for Sanders if he (miraculously) won (I'm sure some of you Clintonite hacks will dispute this), and Maryland (where I live) is really where the black belt starts. Unlike other former-CSA states such as Arkansas, Sanders won the white vote in North Carolina by a convincing margin (52-43), and so he most likely would also be able to drive up turnout among white Democrats and such. Then there's also the populist factor that would lower the margin in the rural areas (as mentioned for Florida's panhandle). Keep in mind that I don't think Sanders would've won NC, I don't even know if he would've beat Clinton's margin, I just think that NC would by no means be a weak swing state for him like Florida.
1. This was a poll of what black people thought of him in April 2017, not during the campaign.
2. Why is being a Clinton hack such a horrible thing, but being a Bernie hack isn't?
