I think Drum has the right idea. First, I believe there are a nontrivial number of elected Democrats who have, to some degree, bought into the benevolent empire notion with respect to the Middle East. Second, it isn't enough to raise the specter of permanent bases in Iraq. We have permanent bases all over the world. Maybe having permanent bases in Iraq is a grand idea, or would be if they were actually operating in a peaceful environment. I don't really have an opinion on that as I don't really have an opinion on the appropriateness of the dozens of other military bases we have around the world.
Still, I think it is necessary to point out that Bush's desire to stay in Iraq forever, while largely dominated by the fact that his ego is entirely invested in the project, is actually due in part to Bush's desire to stay in Iraq forever. That's a rather costly choice we're making as it isn't exactly a peaceful environment. People should be made to understand that.