>public, as evidenced by polls, disapproves of the current situation in Iraq. One may argue that this disapproval comes from an incomplete picture of the situation, but that does not make the concern illegitimate
I might be misunderstanding what you’re trying to say, but this makes no sense to me. How can the "concern" be anything but illegitimate if it is based on incomplete, distorted, and factually incorrect information? Seeking clarification of a policy in order to clear up rampant misunderstanding is understandable, caving in to popular pressure brought on by that misunderstanding is not.

>a Republican senator now sees chance to continue his ‘good’ work cut-short if measures are not taken to address a largely unpopular course of action
Your point about the political realities of the situation is correct. But shouldn’t the "measures" taken by such politicians be ones that improve their constituents’ understanding of the situation, not ones that bend to their uninformed will?

Also, I imagine it would be difficult to "clearly articulate the reasons for war" and keep the public informed when the opposition accuses you of lying every time you open your mouth.