The more successful sons and daughters know when to lean on their parents - and when to go their own way. George W. Bush helped run his father's presidential campaigns in 1988 and 1992. But in his winning campaign for governor of Texas, he never mentioned his father's name in any of his campaign commercials.

Then you get to the last half of the 20th century, Americans are getting very skeptical about their leaders and their institutions, and another place that is affected is parties and conventions.

American political scions evoke a central contradiction in our thinking. We believe - or say we do - in nurture, not nature. Yet we are comforted by the aristocratic notion that leadership might run in the bloodlines.

So the result was that as one approached a political convention for most of the 19th century and for most of the 20th century until the 1960's, part of the drama was the fact that you didn't know ultimately who was going to be the nominee at the end of that convention week.