He ran unsuccessfully for Governor of Connecticut in 1970, losing the general election to Thomas J. Meskill. He continued his career in public service as Director of the Office of Technology Assessment from 1973 to 1977. "For his sustained contributions to science and the national welfare during the years he served as a Congressman," Daddario was awarded the Public Welfare Medal from the National Academy of Sciences in 1976. He served as president of the American Association for the Advancement of Science from 1977 to 1978. He co-chaired the American Bar Association's Association for the Advancement of Sciences and the Conference of Lawyers and Scientists from 1979 to 1989. Daddario was married to the former Berenice M. Carbo. He died on July 7, 2010 from heart failure, according to his son, Richard, the New York Police Department's incoming deputy commissioner for counter-terrorism. At the time of his death he lived in Washington, D.C. Two of his grandchildren, Alexandra and Matthew, are actors.