The real question, Dallek says, is whether Obama can sustain his magnetism in the rough-and-tumble of a modern presidential campaign. "There's an old saying," the historian says. "You can only hold the highest note for so long." If Obama falters—if he loses the nomination in a messy intraparty battle—his supporters are likely to be deeply disappointed and angry. "If he comes undone, there will be a big crash," says a prominent Democratic strategist who has advised Bill Clinton. And that could easily turn the country in a cynical, rancorous direction—spelling the end of Obama rapture.