because now one party can say "we voted to withdraw the troops, just like the American public wants..." and the other party can say exactly what?  We tried to strike the deadline language and they wouldn't let us?  

It's an incremental step, but it's a step forward, and might just make a dent on the D.C. pundit class (hope springs eternal, as usual)--

And Lieberman most certainly no longer counts as a Democrat.  He's Joe (I-CT).