It's probably all of those things. But it's also because young Americans have had Obama — a young, relatively idealistic candidate — to vote for in the past two elections. They've seldom if ever been made to choose between two dull white men running for the nation's highest office. Had they come of age choosing between Gerald Ford and Jimmy Carter or George H.W. Bush and Michael Dukakis, they might have learned by now that good enough is good enough.