Nothing Specter can do if the dems ask to hold over. The dems will suffer nothing from doing so, every dem on the committee is well-protected in their states and supported by lefties who would cheer them.
The only thing that would stop them would be their own humanity -- their own character and sense of what is right, their own belief that their word means something.
Anybody want to take bets on how THAT will come out? I will say that sometimes, democrat senators DO act out of conscience and character, but I don't think they let those senators on this committee.