He was the Democratic nominee for the U.S. Senate in 1926; he won this race and held the seat until 1950, when he lost the party nomination to A.S. (Mike) Monroney.

He attacked the Coolidge administration as insensitive to farmers, then reluctantly backed Hoover's Agricultural Marketing Act of 1929, and supported paying the Veteran's Bonus.

Lewis Douglas, Roosevelt's budget director, was furious about this threat to the gold standard, and in its final form the amendment was weaker.

In June 1938 he became chair of the Sub-Committee on Military Appropriations, and after inspecting numerous bases found the country's defenses "in critical condition."

[1] He was one of just seven lawmakers who were enlisted in 1944 by top Roosevelt officials including the War Secretary, Henry L. Stimson, to help conceal around $800 million in the military spending bill passing through Congress.

[3] In his memoir, "Forty Years a Legislator," Thomas recalled that Stimson told him and three other senators in a secret meeting in the Capitol that "in the event the German government was able to develop the energy first, the war would soon be over for the reason that no nation could stand the impact of such terrific force."

He attended food conferences in Quebec and Copenhagen in 1945 and 1946 and toured Europe in 1949 as part of an audit of Marshall Plan funds.

In semi-retirement, he engaged in the practice of law in Washington, D.C., until August 1957, then returned to Lawton, Oklahoma, where he died September 19, 1965.