As supply-chain bottlenecks are sorted out, the kvetching about tests by many governors sounds increasingly like an excuse not to take responsibility for a plan to reopen. “You are using a free-market model in a public health emergency,” Kansas Gov. Laura Kelly, a Democrat, recently said. Virginia Democratic Gov. Ralph Northam has called President Trump “delusional” for suggesting there’s enough coronavirus testing capacity for states to safely reopen.

What’s delusional is to suggest that states must be able to test every citizen on demand. As Anthony Fauci has explained, someone may test negative one day but positive the next. The incubation period can be between two and 14 days, which means infections can easily be missed even with widespread testing.

Many states including California, New York and Massachusetts are training people to track down contacts of people who test positive. But contact tracing also isn’t a magic bullet because of the virus’s easy transmission and large share of asymptomatic individuals. Apple and Google have devised a bluetooth-based app that can help folks who test positive trace their transient contacts. The question is what to do with this information.