As was entirely inevitable, David Brooks is beginning to turn on Obama in favor of McCain. His article, however, points out a worrying fault line in the Obama campaign, which is that "unity" simply isn't that robust a foundation for his appeal. I don't think Brooks is quite right to associate unity with senseless bipartisanship of the type we saw among the "Gang of 14," but there's no doubt that the litany Brooks offers up will undercut Obama's claims to post-partisanship, particularly against McCain. That's why it's good that Obama is moving towards a more concrete appeal centered around McCain's plan for a 10,000 year occupation of Iraq, a continuation of Bush's plutocratic neoconomics, and all the rest. Hillary is considered a divisive figure, but McCain isn't, so you're not going to get very far against him by arguing that you're the sole force capable of bringing the country together. But while Obama has gone abstract against Hillary because they largely agree on matters of substance, McCain is the champion for all manner of unpopular and discredited policies, and one can make a very sharp, and very concrete, argument against the actual vision he has for the country.