I haven't seen an explanation of why not a single Senate Republican was willing to filibuster the Iraq budget authorization last week. My understanding is that while filibusters arent' allowed for the final joint House-Senate authorization, they were allowed at the previous stage, and any single Senator could've filibustered, requiring a vote of 60 Senators to overcome it.
So are the Republicans really opposed to ending the war, or not? I'm not sure that relying on a presidential veto is a sufficient answer for them. The money has to come through sometime, so the whole process will just get repeated. Maybe the Republicans just figured that a filibuster woudn't stop anything because the joint bill would come back with a timetable, anyway. Still, a filibuster would have added a roadblock to the process.
I'm open to the idea that Republicans with a political future extending through 2009 might not want the Iraq debacle to follow them indefinitely, and might try and pin it on Bush, have it collapse during his administration, and claim the rest of the party wasn't responsible. Not sure if this is the case, but I hope they try it.