Tonight on the Last Word: Republican governors urge people to wear masks as Trump refuses. Also, David Frum explains why U.S. institutions failed under the Trump presidency. Former Vice President Joe Biden commemorates Memorial Day in Delaware, making his first public appearance in over two months. Plus, Pulitzer Prize-winning journalist Laurie Garrett answers questions from viewers about the coronavirus. And presidential historian Jon Meacham talks to Lawrence about his new podcast “Hope, Through History,” which explores how the U.S. fared through past crises. Dr. Vin Gupta, Zerlina Maxwell and Jonathan Alter also join Lawrence O’Donnell.