Returning to Massachusetts, he entered politics and served as selectman, assessor, and overseer of the poor in Wareham from 1920 to 1925. He served as a delegate to all Republican state conventions from 1924 to 1947; served in the
Massachusetts House of Representatives in 1925 and 1926; as a member of the
Massachusetts Senate from 1926 to 1947, and as
president of the state senate in 1946 and 1947. He was elected as a Republican to the Eightieth Congress to fill the vacancy caused by the death of United States Representative
Charles L. Gifford, and reelected to the five succeeding Congresses (November 18, 1947 – January 3, 1959). Nicholson voted in favor of the
Civil Rights Act of 1957. == Personal life ==