Nobody is talking about it, but the Democratic Party is in dire straits—really dire straits. Its future depends on a sweeping reorientation, both toward its traditional roots in the working class and toward the prospects of America’s changing demographics. Yet that needed reorientation requires vision that is not in the wheelhouse for its frontrunner presidential candidate, Hillary Clinton, for the outgoing President Obama, or for the inside-the-beltway party leadership as exemplified by Democratic National Committee Chairwoman Debbie Wasserman Schultz.      Only a new generation of party leaders, willing to forego the wedge issues of identity politics...