He is hailed by his supporters as the hope of an increasingly multicultural nation, a political phenomenon who can wow white voters while carrying the aspirations of African-Americans all the way to the White House. So why are some black voters so uneasy about Senator Barack Obama? The black author and essayist Debra J. Dickerson recently declared that “Obama isn’t black” in an American racial context. Some polls suggest that Mr. Obama trails one of his rivals for the Democratic nomination, Senator Hillary Rodham Clinton, in the battle for African-American support. And at the Shepherd Park Barber Shop here, where...