If Barack Obama disappoints his supporters, they will have only themselves to blame. In January 2007 Mike Huckabee, a former governor of Arkansas, said he was running for president to revive “our national soul”. He was not alone in taking an expansive view of presidential responsibilities. With the exception of Ron Paul, all the serious candidates waxed grandiloquent about their aims. John McCain said he modelled himself on Teddy Roosevelt, a man who “nourished the soul of a great nation”. Hillary Clinton lamented that America had no goals, and offered to supply some. And let us not forget the man...