Lincoln Chafee wrote an op-ed in Thursday's New York Times pointing out the existence, pre-AUMF, of a now-frequently-overlooked "third way":

As someone who was in the Senate at the time, I have been struck by the contours of the debate. The situation facing the candidates who cast war votes has, to my surprise, often been presented as a binary one — they could either vote for the war, or not. There was no middle ground.

On the contrary. There was indeed a third way, which Senator James Jeffords, independent of Vermont, hailed at the time as "one of the most important votes we will cast in this process." And it was opposed by every single senator at the time who now seeks higher office.

The third way in question was the Levin amendment to S.J. Res. 45 (which was later abandoned in favor of the identical H.J. Res. 114 [which is now Public Law 107-243 {which is better known as the Authorization for the Use of Military Force in Iraq}]). Essentially, the amendment encouraged the president to exercise a bit of diplomatic restraint; it didn't bind him to the U.N., exactly, but it certainly reinforced the value of acknowledging the international community. Needless to say, the amendment failed (24-75), and here we are four years later.

As the block quote notes, every senator now running for the White House voted against the Levin amendment four years ago. In fact, a list of the highlights from the "75" side of that vote would include (and this is just a sample): Joe Biden, Hillary Clinton, Tom Daschle, Chris Dodd, Russ Feingold, Bob Graham, Chuck Hagel, Joe Lieberman, Harry Reid, Chuck Schumer, and, alas, my buddy John Edwards. It's entirely possible that each of those guys has an excellent and principled explanation for his or her opposition. Maybe, for instance, the amendment contained some sort of preposterous earmark, or perhaps an egregious spelling error. But as The Linc points out, there's no way to be sure, because none of those guys has ever really been asked about it. And that seems a pity.