in a rational world, this would get harry reid to take back all the concessions he made to get lieberman's vote and then use reconciliation to force the bill through with a 50 vote majority.
but we don't live in a rational world. or at least harry reid doesn't.
there has been a lot of hostility directed at lieberman for demanding concession after concession to get his vote. but if harry isn't willing to pull the reconciliation trigger, what incentive does lieberman have to not demand everything he wants? yes, lieberman is a terrible senator, but given that lieberman is lieberman, why would he compromise when there is no risk to not compromising?
UPDATE: i didn't see what yglesias said until after i wrote the above post. he makes a similar point.