today, trump's own testing czar said that's not true. >> we're learning every day, but nobody lies to the american people. we're completely transparent and honest. >> reporter: four former heads of the cdc warning in "the washington post" -- sound science is being challenged with partisan potshots, sowing confusion and mistrust at a time when the american people need leadership, expertise, and clarity. and biden's message today, follow the science. >> mr. president, please listen to your public health experts instead of denigrating them. do your job, mr. president. >> mary bruce with us tonight. mary, president trump dealing with two crises at once. the pandemic which you just reported on there and the national outcry sparked by the police killing of george floyd. we know the president was asked by cbs about black americans being killed by police, and here's how that question played out. >> why are african-americans still dying at the hands of law enforcement in this country? >> and so are white people.