Every Democrat agrees that a brokered convention in Denver would be disastrous to the nominee, and Hillary has argued that "pushing" her out of the race would cause a defection of her supporters. It seems that the Democratic party and its superdelegates are trying to identify their moment of diminshing marginal returns. In the context of this primary, that is when Hillary's continued presence causes more damage to Obama than publicly dismissing her by uniting behind him.
The Clinton campaign perceives this balancing act and is exploiting it by matching her indefinite presence with increasingly divisive, and potentially destructive rhetoric. Take for example yesterdays comparison of Florida and Michigan to Bush v. Gore 2000, the women's suffrage movement, even Zimbabwe. She is taking an inter-party issue, falsely elevating it, and splicing herself to its outcome. The talking point goes, "Reject Hillary now and lose Florida and Michigan in November." She is currently controlling the narrative on this story, and the closer the primary process comes to its natural conclusion, the more she will challenge Obama's legitimacy, thereby threatening his prospects in November.
I don't think that the tipping point has occured, but it is close. Obama was going to lose West Virgina and Kentucky, so it was better to lose to a person that was actively campaigning. I think that the May 31 rules committee meeting is the breaking point. No matter what the committee decides, the appearance of indecision on the part of the superdelegates beyond that date will embolden Hillary and do more damage to Obama than effectively ending the contest now.
The superdelegates will have to take action if a Democrat is to be elected in November. Obama cannot spend the summer campaigning against the backdrop of a wild eyed Hillary bellowing claims of voter disenranchisement and civil rights violations. It is becoming clear that Hillary is willing to torpedo Obama and the Democratic party if she does not get her way. I hope that the superdelegates appreciate the situation and take appropriate action.
N.B. This is not a partisan issue. If the superdelagates want to throw this to Clinton, the time is now. Overturning the results of the pledged delegate contests would be destructive, but if that's what the superdelegates want to do, Clinton would need time for damage control. The sooner the superdelagates announce the better.