Sorensen was devastated by Kennedy's assassination, which he termed "the most deeply traumatic experience of my life. ... I had never considered a future without him." He later quoted a poem that he said summed up how he felt: "How could you leave us, how could you die? We are sheep without a shepherd when the snow shuts out the sky." He submitted a letter of resignation to President Johnson the day after the assassination but was persuaded to stay through the transition. Sorensen drafted Johnson's first address to Congress as well as the 1964 State of the Union. He officially resigned February 29, 1964, and was the first member of the Kennedy Administration to do so. As Johnson was later to recount in his memoirs, Sorensen helped in the transition to the new administration with those speeches.