Democrats in Congress have a cure for the coronavirus crisis: a nationwide paid sick-leave mandate. Sen. Patty Murray of Washington says this new benefit would allow people to “focus on staying healthy and preventing the spread of this disease.” Her House sponsor, Rep. Rosa DeLauro of Connecticut, said the lack of such a mandate could “make coronavirus harder to contain.”

Ms. Murray and Ms. DeLauro began advocating such a policy in 2004 and have clearly internalized Rahm Emanuel’s immortal political advice that “you never...