Richard Helms resigned as Director of the Central Intelligence Agency in early 1973. Casey, once an intelligence officer himself, resigned from the SEC to seek the CIA position. Through friends, Cook made it known that he wanted to be chairman of the SEC. He won the backing of both White House Chief of Staff H. R. Haldeman and Assistant to the President for Domestic Affairs John Ehrlichman. Cook was nominated by President Richard Nixon, approved by the United States Senate, and sworn in as SEC chairman on March 3, 1973. He was the youngest person ever to lead a federal agency.