Clancy contested numerous elections for the Communist Party, and was on the central committee executive during the 1968 split after the Soviet Union's invasion of Czechoslovakia. He resigned from the party in 1971, and in December of that year became president of the new Socialist Party of Australia. Disagreement among members led to his removal and resignation from the party in 1983. Attempting to reunite the far left, he formed the Association for Communist Unity in 1984.