In 1978, Dlouhý joined the Communist Party. In the third week of the November revolution of 1989 he was nominated as one of 10 Communists to the government of Czechoslovak Socialist Republic and on 10 December 1989 he was appointed Deputy Prime Minister of the federal government (the Government of National Understanding) where he also served as a Chairman of the State Planning Commission. In December 1989, he quit the Communist Party.