Power has the right thread on this. If the Obama campaign retreats it is dead because if they get to the convention and the Clintons can win by Super delegates alone then they will do anything to do it. The Clinton’s can not afford to really have people and Democrats remember the worst of the Clinton years.
The only way Clinton can win is to depend on SuperDelegates. She would have to claim over 90% of the remaining delegates to win any other way (assuming she keeps the supers she already has).
But, the same is true for Obama. He has to win over 70% of the delegates remaining, and the way the Democrats divide delegates, a 60/40 split is a huge win.