Nearly 500 national security experts – both civilians and former senior uniformed officers — have endorsed Joe Biden for president, saying the "current president" is not up to "the enormous responsibilities of his office." Others who signed on to the letter include former State Department Deputy Secretary Richard Armitage, who served under George W. Bush, as well as Democratic stalwarts like former national security adviser Susan Rice, former Secretary of State Madeleine Albright, and former senior Pentagon official, Michele Flournoy. The pro-Biden letter comes on the heels of an endorsement of Trump last week by 235 senior military leaders, saying the president has rebuilt the military and is a "strong advocate" for military personnel and veterans.