Over the course of the Bush administration, it became convenient for a lot of traditional realists and traditional foreign policy liberals to make common cause against neoconservative and liberal hawks alike. Hence you had odd spectacles like Zbigniew Brzezinski's rise as a leading foreign policy voice, when years before he was Carter's resident hawk and a bete noire of liberals, and Anatol Lieven and John Hulsman collaborating on Ethical Realism: A Vision for America's Role in the World
. And it's continuing on after the election, with Robert Gates likely to remain at Defense and Brent Scowcroft proving an influential Obama adviser. As Matt says, that all makes a certain amount of philosophical sense. Serious realists and serious liberal internationalists actually have a great deal in common, while liberal hawks and neoconservatives agree on an awful lot. But at some point, this alliance will probably break apart, as realists and liberals also disagree on an awful lot. My hunch has always been that it will erode when a liberal president first tries to exercise military power, as lots of liberals who opposed Bush-era invasions will find Obama's efforts congenial enough, and it will do so quietly. But if the administration has a lot of liberals and a lot of realists, the split could be noisier, and characterized by more infighting. Or maybe an actual synthesis will be reached. It's hard to say.