sidney blumenthal has been clinton's closest adviser for twenty years - to the point that i wouldn't be surprised if they've had a few nights together. there was a fiasco when she tried to bring him into the state department; obama hates him. if she wins, he's going to get a super plum post. maybe even chief of staff. so, it's maybe a little bit of a stretch to suggest he's just there to clean up the mess. regardless of everything else, you are likely to be hearing a lot from sidney blumenthal for the rest of the cycle - and even more from him if she wins. so, while i agree that the situation is curious, i think this is grasping at straws.
in the grander scheme of things, they have to be able to grasp just how much credibility this would give to sanders. trump is in the process of selling out. if they go through this process, sanders is going to come out of it bigger than jesus. what i mean is that they're figuratively martyring him. he's going to start swinging trump voters, and he could be competitive in places that nobody would even consider.
they may be arrogant and everything, but they can't be that stupid.