If "Black" Is A "Race" Then So Is "White"

For the Limbaughs and Buchanans and fellow travelers who are trying to reduce General Powell to (their essentializing version and warped understanding of) a black man: Have any white persons who have decided to endorse a candidate who happens to be white over a candidate who happens to be black been asked if they chose the white candidate because they were white? And if not, why not?