Tonight's convention theme is One Nation. Yet more and more, Team Obama seems to be playing the economy card by running a "Two Americas," class-warfare campaign not much different than if John Edwards had been the nominee. There is nothing postpartisan about Joe Biden, a class warrior without peer. Obama, Dem insiders say, needs to heighten his appeal to working-class whites, and it's my guess that Biden was ultimately seen as a better vehicle for that than Hillary Clinton. Yet outside of the Delaware delegation, it's tough to find too many folks excited by Biden. So why should independents, then, see Biden as a plus?