They can either disenfranchise about 50% of their supporters (blue collar, whites, older workers) and go with Obama. Problem is they will stay home and McCain will win.
OR
They can disenfranchise about 50% of their supporters(college educated, blacks, younger workers) by choosing Clinton and have them feel ignored and cheated and stay home and the dems loss to McCain.
What the party leadership is doing is hoping that itll all play out and a choice will be made without their hand being seen. (ie someone running out of money). That way they dont loose 50% of their supporters.
The democrats can win this year, Bush has made that a real possibility. But they cant if they tear themselves apart and half their voter base stays home. I dont think the DNC will step in till the very last second, just before the convention.