He traveled to Texas in 1878 to edit the Crockett Patron. After a year he edited the Corsicana Observer and established the Independent there. In 1880 he moved to Austin, where he was associated with the Austin Statesman. The Houston Post secured his service as correspondent to cover the state capital. Johnston was chosen editor-in-chief of the reorganized Houston paper in 1885, and later he became president of the Houston Printing Company. As an editorial writer he was quoted by the press throughout many states. For two years he was first vice president of the Associated Press.
Johnston was one of the leaders of the Democratic party in the South. He declined the nomination for lieutenant governor of Texas in 1898. From 1900 to 1912 he was a member of the Democratic National Committee. Early in 1913 Governor Oscar B. Colquitt appointed him United States senator to fill the unexpired term of Joseph W. Bailey. Johnston served from January 4 to February 2, 1913, when he returned to Houston and resumed his duties as active head of the Post. He retired in 1919 and served as state senator from the Houston district; he resigned when he was appointed chairman of the state prison commission by Governor William P. Hobby on January 12, 1920. Johnston married Mary E. Parsons in 1875, and they had three children. He died on February 28, 1926, and was buried in Glenwood Cemetery, Houston.
29° 45.835, -095° 23.198