I tend to believe that it was a combination of the Dem spin/attack machine (already geared-up for the midterm election), the anti-Bush MSM (already geared-up for the midterm election), spineless Republicans afraid of the above (already geared-up for the midterm election), and (even including) a good number of folks, radio talk show hosts and FReepers who were either unwilling to allow themselves to be perceived as weak on national security, or opposed it for selfish reasons, or were merely duped. Don't discount the last category.
I think most of the guys on 'our side' were so quick to move because of fear.........fear of seeming weak, fear of being out maneuvered by the left, fear of losing in November........all that, and more.
The irony is, I think they have behaved more weakly in trying to puff up their chests, and have actually hurt their chances of reelection in November because of this hysteria driven debacle.
We obviously will have to wait and see how it pans out, but IMO, it has hurt far more than it has helped. Not to the point of losing the Senate or the House perhaps, but definitely to the point of losing seats, and more importantly the respect of their constituents.
We expect leaders, not emotional reactionaries.