As the Rev. Jeremiah Wright gleefully tours the airwaves, inflicting severe political damage with almost every utterance, he is proving that racism isn’t the only obstacle to a black president. That historic prize is almost within the grasp of one of the most talented politicians America has ever seen. Yet what seems most likely to frustrate Senator Barack Obama now is not white prejudice but the frivolity, egotism and pettiness of those who should be his most serious and dedicated supporters.