We know that 60 votes are needed in the Senate to pass cloture (start and end discussion), but only 51 are needed to pass the bill if cloture is approved.

If all those Dems who have said they oppose the Dream act, vote FOR cloture but against the actual bill, it will pass. They will vote againt the actual bill to tell voters "I voted against amnesty". I can see Obama right now calling the Dem senators and asking them to do exactly that. He might be calling the Republican fence sitters also.

When we call we need to make sure these fence sitters will vote against cloture also.