 Historically , justices have come from some tradition of public service ; only George Shiras , Jr. had no such experience . Relatively few justices have been appointed from among members of Congress . Six were members of the United States Senate at the time of their appointment , while one was a sitting member of the House of Representatives . Six more had previously served in the Senate . Three have been sitting governors . Only one , William Howard Taft , had been President of the United States . The last justice to have held elected office was Sandra Day O 'Connor , who was elected twice to the Arizona State Senate after being appointed there by the governor . 
