What they will be left with, if anybody is left with anything, is an argument that while they thought it should be left on the table, they didn't ever really mean for him to use it ----- or that they wanted him to do other things first --- or some other nonsense that will sound just as convoluted as their excuses about the Iraq war resolution did in the last election.
This actually isn't a hypothetical question, you see. George W. Bush is doing this as we speak. The question today is, "Do you believe he has the right to attack Iran preventively or don't you?"
Politicians apparently feel they must say that they can't take any options off the table. But there is no reason they must go before a particular political constituency and forcefully imply that they would use the Bush Doctrine against Iran if it failed to meet certain conditions. The Bush Doctrine must be repudiated not reinforced. Until we restore the post WWII international legal consensus against wars of aggression, we are going to be attacking countries who quite rationally have decided that they are better off getting nukes while the getting's good.
The Bush Doctrine is not a non-proliferation policy. It's a recipe for disaster and until Bush is out of office it pays to remember that he's the guy who can pull the trigger. It's not a good idea to say things that anyone, including Bush, may very well see as an endorsement of doing that.
http://digbysblog.blogspot.com/2007_02_01_digbysblog_archive.html#117046464485756663