Johnston is frequently cited as having served in the North Carolina Senate in 1779, but this is not confirmed by a careful perusal of the Senate Journals. He may have been elected but he certainly did not attend. In Johnston's own words, after 1777 he "had nothing to do with public business" during the Revolution except for his later service in the Continental Congress. Under the new state Government, Johnston was elected to the North Carolina Senate in 1783 and 1784.