The trouble for Clinton and the Democrats generally is that while Barack Obama was able to unite the factions of the left to get himself elected, it’s not clear anyone else can.

Obama wanted to be a Reagan of the left, a “transformative” president who moved the magnetic poles of American politics leftward. The jury is out on that project, but he did succeed in at least one sense. Reagan united foreign policy hawks, social conservatives and economic conservatives — the famous three legs to the stool of the conservative movement.

Obama did something very similar on the left. He united the civil rights or identity politics wing, the economic or egalitarian wing and the more elitist technocratic wing. Obviously, these movements overlap — just as the different factions of the Reagan coalition overlapped — but each has its own priorities and passions.