Joe Biden had his best debate on Sunday night, his first time mano a mano against Bernie Sanders, who stood a healthy six feet to Mr. Biden’s left. Mr. Sanders argued the U.S. is unprepared for the coronavirus pandemic, since it has “thousands of private insurance plans” instead of a centralized health-care system.

“With all due respect to Medicare for All,” Mr. Biden said, “you have a single-payer system in Italy. It doesn’t work there.” That day alone, Italy reported 368 coronavirus deaths, the highest daily figure then...