A few weeks ago, the Rev. Jesse Jackson made something of a fool of himself. There he was -- a historical figure in his own right -- threatening the castration of Barack Obama. It was sad to see.

If I have often criticized Mr. Jackson, I have also, reservedly, admired him. He is a late 20th century outcropping of a profoundly American archetype: the self-invented man who comes from nothing and, out of sheer force of personality, imposes himself on the American consciousness. If he never reached the greatness to which he aspired,...