THIS time last year it looked as if Hillary Clinton's path to the Democratic nomination would be a cakewalk. She had the best brand-name in American politics. She controlled the Democratic establishment. She had money to burn and a double-digit lead in the opinion polls. And as the first American woman to have a chance of breaking the presidential glass ceiling, she had a great story to tell. And Barack Obama? He was a first-term senator with few legislative achievements and a worrying penchant for honesty (in his autobiography he admitted to using marijuana and even cocaine, “when you could...