Slaughter was elected as a Democrat to the Seventy-eighth and to the Seventy-ninth Congresses (January 3, 1943 – January 3, 1947).
He was an unsuccessful candidate for renomination in 1946 to the Eightieth Congress.
He served as member of the State Democratic Committee from 1960 to 1962.
He resumed the practice of law in Kansas City, Missouri.
He was appointed magistrate judge of Lafayette County in 1972.
He died, June 2, 1974, on his farm near Odessa, Missouri.
He was interred in Greenton Cemetery, Odessa, Missouri.