Second, the argument understates the radicalism of what Sanders and Warren propose. Theirs is not a painless policy massage in the direction of a kinder, gentler economy. It’s a frontal and highhanded assault on American capitalism. If it succeeded, it would entail devastating dislocations to millions of workers lasting for years. If it failed, it would have devastating effects on the country lasting for decades.

How devastating? In October, Brian Riedl of the Manhattan Institute tallied the costs of Mr. Sanders’s policy goals. By his calculations, the federal government would double in size. Half the American work force would be employed by the government, Mr. Riedl writes. Government spending as a percent of G.D.P. would rise to 70 percent (in Sweden, it’s less than 50 percent). The 15.3 percent payroll tax would hit 27.2 percent to help pay for Medicare for All. Total additional outlays would reach $97.5 trillion on top of the nearly $90 trillion the federal, state and local governments are projected to spend over the next decade.

At least Sanders is honest enough to call this what it is: socialism. Warren’s terminology is less forthright. Her ambition is no less breathtaking.