and author of Fighting Back the Right: Reclaiming America from the Attack on Reason.
The Democrats' dilemma is that Sanders is the only alternative they have this year. Talk of parachuting in "Uncle Joe" or someone else is the same sort of fantasy talk that the RNC was entertaining a few weeks back. Discarding the whole primary vote process in favor of some last-minute back-room deal would turn most of the Democratic base against the party and incur massive down-ballot repercussions. It's something they simply cannot do.
Then there's the problem that it's "her turn" and Hillary won't go quietly. It's been obvious from the start of the whole Kabuki Theater e-mail "investigation" will go nowhere because Hillary has enough dirt (and the vindictiveness to use it) to take down Obama and most of his administration with her if they try to take her out that way. I'm sure they've tried negotiation, but Hillary and Bill know this is their last gasp and they'd rather go down fighting for power than step aside.
So the powers-that-be are being forced to let her run into the Trump buzz-saw. It won't be pretty, but it's the only way out.