After Barack Obama’s defeat in Pennsylvania, David Axelrod, his campaign manager, brushed it off: “Nothing has changed tonight in the basic physics of this race.”

He may well be right  but what a comedown. A few months ago the Obama campaign was talking about transcendence. Now it’s talking about math. “Yes we can” has become “No she can’t.”

This wasn’t the way things were supposed to play out.

Mr. Obama was supposed to be a transformational figure, with an almost magical ability to transcend partisan differences and unify the nation. Once voters got to know him  and once he had eliminated Hillary Clinton’s initial financial and organizational advantage  he was supposed to sweep easily to the nomination, then march on to a huge victory in November.

Well, now he has an overwhelming money advantage and the support of much of the Democratic establishment  yet he still can’t seem to win over large blocs of Democratic voters, especially among the white working class.