Moore was a frequent political candidate of the Socialist Party. In 1928 he ran for the US Congress in New York's 21st congressional district. In 1934, Moore ran on the Socialist ticket for Chief Judge of the New York Court of Appeals. In 1935, he became the organiser for the International Labor Defense in the New England Territory. He used his position in that organisation to speak on behalf the Scottsboro Boys, a case in which nine young African-American males were accused of raping two young European-American women.