She’s the candidate with a plan for everything: That’s Elizabeth Warren’s brand. But even that sells her ambitions short, as we discovered after a tour of her 60-some policy papers. Ms. Warren is proposing a transformation of American government, business and life that exceeds what the socialist dreamers of a century ago imagined.

Her standing in the polls has fallen after missteps over Medicare, but she is still in the top candidate tier. Her ideas deserve to be taken seriously because they show where the American left wants...