To wit: Warren says she can deliver a generous Medicare-for-all plan with only $20.5 trillion in additional federal spending. That’s a quarter to a third less than any serious estimate of the plan from outside her campaign. How will she get there? Why, by slashing administrative costs and then mandating that everything else cost less. Warren is not exactly the first progressive reformer to have this same idea, and if she pushes forward with it, she will be but the next in a long line to discover that she can’t make it work, politically or economically. As Philip Klein of the Washington Examiner dryly noted, Warren could just as well have written that Mexico was going to pay for her big, beautiful plan.

Warren’s revenue ideas are, if anything, even more exquisitely incredible. Take her proposed wealth taxes — no, not the 3 percent ultra-millionaire wealth tax she has already pledged for other things, but an entirely new 3 percent tax on all wealth over $1 billion. The tax would, Warren says, raise $1 trillion over 10 years.

The assumption is typical of her whole plan. Because on one level the math does work: The United States has about 600 billionaires, and by my calculation, the total value of their wealth-taxable assets would be something under $3 trillion. Three percent of that, collected 10 times, should indeed yield nearly $1 trillion.