I think even if that statement is probably true, that it is also extremely ignorant. How can you prove that black people only voted for the black president because he was black?
Perhaps (i dont believe this for a second) that most Americans are informed voters?
A more likely explanation would be that Americans are excited for change. Consumer studies show that Americans are generally more excitable as spenders over new products. So whats wrong with applying that principle to politics? As someone stated earlier, fresh ideas come from fresh minds.