Today's must-read link is Ezra Klein on the politics of branding.
Although Democrats have often been called the party of identity politics (in the sense that a significant part of Democratic party politics has been built around a coalition of 'identity blocs' such as women, gays, Latinos, etc), Ezra contends that actually it's the Republicans who have done a much more complete and successful job of it:
Over the past 30 years, Republicans have successfully merged identity with politics, the importance of which is almost impossible to overstate. When your party affiliation becomes enmeshed with your sense of self, attacks on your candidate become attacks on your person, and thus ends any hope of being convinced out of your position. No longer are you dealing with policy or evaluating arguments, now your personal defenses are up, your worth is being called into question, and the rightness of your original position is transcendentally important.
And he's got a really good point. One big problem with identity politics as practiced by Democrats has been that it has not yet managed to promote a sense of overall party unity.
In some ways the Republicans have had it easier. Their membership is not very diverse, so it's easier for them to create that feeling of commonality that has allowed so many republicans to feel their political identity is a part of their core self. Democrats have not done a very good job of convincing people that, say, a working-class Latino union member and a tenured gay university professor have a true common cause despite all the surface differences. It's certainly not an easy job, but it's more and more obvious that it is a vital one.

