Should I vote for someone because I identify with him?

Obama’s ‘not one of us’ attack on Romney echoes racial code by Karen Tumulty, who might say "to be sure" before adding:

The context of the ad is very different from the one in which the phrase “one of us” was used to divide the country along racial lines....

But anyway, why must people identify with a particular candidate? Don't appeals to identity (which certainly do suggest racism to me) mean that a candidate doesn't have much to say on the issues?