I understand the rough and tumble of politics. But Barack Obama -- the supposedly postpartisan, postracial candidate of hope and change -- has gone where few modern candidates have gone before.

Mr. Obama's campaign is now trafficking in prejudice of its own making. And in doing so, it is playing with political dynamite. What kind of potential president would let his campaign knowingly extract two incomplete, out-of-context lines from two radio parodies and build a framework of hate around them in order to exploit racial tensions?...