The White House must find a way to keep working and show that the government is still operating notwithstanding illness or the absence of the president, a group of former chiefs of staff said on Friday morning. A bipartisan panel brought together for a virtual event by the Center for Presidential Transition said that President Trump and first lady Melania Trump’s positive coronavirus tests underscored the importance of establishing practices that, when needed, can continue without the president, because the work and problems of the nation don’t go away.