If Mr. Obama, Mr. Bush, Mr. Clinton and Mr. Carter were to start an effort together without Mr. Trump, a former Obama aide lamented, the endeavor would be entirely eclipsed by the fact that they did it without the sitting president. Mr. Trump has clearly enjoyed humiliating his predecessors and has called Mr. Bush’s invasion of Iraq “the single worst decision ever made.” In a mid-March tweet, just as the nation’s economy was shutting down and schools were closing, Mr. Trump wasted no time criticizing his predecessor’s management of a previous health crisis. He railed against Mr. Obama’s response to the H1N1 swine flu and called it “a full-scale disaster, with thousands dying, and nothing meaningful done to fix the testing problem, until now.”

Mr. Bush recently wrote a note to his staff that was obtained by The Dallas Morning News. He expressed “absolute confidence in the experts who are in charge” of the nation’s coronavirus response. He said that he was “reading, painting and riding mountain bikes” and that he and his wife, the former first lady Laura Bush, were “handwashing and social-distancing to the max.”

But wouldn’t it be better if he and the other ex-presidents could put the lessons they learned in office to lift the country’s spirit during this unprecedented public health crisis?