My read is that question is 100% dependent on Specter.
If Specter chooses to oppose Alito, even mildly, not only is Alito toast, but the Nuke/Constitutional option will fail to gain the votes needed.
Well if Specter is a concern, then all PA Freepers ought to contact Specter and urge him to support Alito, and work against any Democratic efforts to kill him either in committee or by a filibuster.