He could somehow win black voters and urban white voters? But if you'd asked the same thing about Donald Trump in late 2012, what would any of us had said?
It all depends on context
So you are literally just saying "but Trump" and "blacks/Millennials", without addressing any of the counterpoints to that.
Also how does he win Iowa or New Hampshire that way?
I'm indicating that it would be difficult for him to build a winning coalition and that we have no idea. Anyway, my actual thoughts.
-Among the first four states, NH and SC are the only ones he has a chance of. He could possibly win Southern NH by enough to cancel out the northern parts of the state, and get a small plurality there. Then, momentum would get him a decent-sized SC win. This leads to this sort of map:
Kirsten GilibrandKamala HarrisKanye West
Sherrod BrownSo Kanye wins on a black-young coalition by being Bernie with appeal to African-Americans, I guess.