Johnson was elected as a Democrat to the Sixty-eighth and to the eleven succeeding Congresses and served from March 4, 1923, until his resignation on July 17, 1946.

He is a typical southern Democrat in that he has stood staunchly behind the Administration's foreign policies and has supported most New Deal measures, except on such matters as labour.

He made one of the most eloquent speeches in support of the unamended Lend-Lease Powers Act.In his legislative role Johnson was most famous for his part in the passage of the Radio Act of 1927, stating that American thought and American politics will be largely at the mercy of those who operate these stations.

[If] a single selfish group is permitted to ... dominate these broadcasting stations throughout the country, then woe be to those who dare to differ with them."

]Johnson was appointed by President Harry S. Truman to be a judge of the United States Tax Court, holding this office from July 1946 until his retirement in September 1956.