On May 8 , 2017 , while testifying before a Senate committee , former Director of National Intelligence , James Clapper concurred under oath when asked by Senator Chuck Grassley , a lesson learned , was people at the DNC should have cooperated with the FBI 's investigation of the hacking of its server , instead of stonewalling them .
In connection with the 2016 Democratic National Committee email leak , Senator Chuck Grassley asked James Clapper what the lesson learned was .