This is slightly premature, unfortunately. Obama is at the beginning of his second mandate, which means he has very little to lose, but his track record on the subject is that he delegates away everything he can, so it's the Dem establishment which will decide who comes next, depending on how they view their electoral chances in the next cycle (and of course, whose money they might not get in 'campaign contributions' if they sway too much one way or the other). It could have been easier in 2015, maybe.
In optimistic terms, however, it could be where the wave broke: in the same day, we've had the TSA admitting their job is pointless and Alexander being sacked. It could be that Obama just decided he won't go down in history as the guy who took the Nobel prize and proceeded to screw the country he was entrusted with, f*ck the party... he's a lame-duck anyway and never built a real power base to protect, his star power was always coming from people and media.