It is only natural to vote for someone who one feels is sympathetic to ones own being. You vote for someone who is like your next door neighbor (the one you like, of course.) and you chear for people like yourself when the compete with others.
One shouldn’t black-Americans vote for Barak Obama with whom they can feel unique kinship?
Why shouldn’t veterans vote for Senator McCain with whom they have a lot in common?
Even though neither being black, nor being a veteran gives one electability credentials, identifying with them may well be enough of a reason to vote for one or the other.