At the center of Joe Biden’s health-care proposal is the “public option”—a government insurance policy that would compete with private plans. Mr. Biden has obviously seen the polling. By 57% to 37%, Americans reject the idea, put forth by some of Mr. Biden’s Democratic rivals, of abolishing private insurance in favor of “Medicare for All.” The public option seems like an attractive alternative—enough so that Mr. Biden, in announcing his plan Monday, revived a discredited Obama slogan: “If you like your health-care plan, your employer-based plan, you can keep it.”

Yet...