Thomas was elected
mayor of Gooding in 1917 for a two-year term, and was a member of the
Republican National Committee from 1925 to 1933. He was appointed to the U.S. Senate for the first time in 1928 to fill the vacancy caused by the death of his political mentor,
Frank Gooding, by
Governor H. C. Baldridge. Thomas won the special election later that year to finish the four years of the term, and chaired the Senate Committee on Irrigation and Reclamation from 1929 to 1933. Losing support from the progressives late in the term, he was defeated for re-election in 1932 by
Democrat James Pope. After his 1932 defeat, Thomas resumed his former business pursuits. He was appointed to the Senate again in 1940, this time by Governor
C. A. Bottolfsen, to fill the vacancy caused by the death of
William Borah, the
dean of the Senate. Thomas won another special election to finish the term later that year, and was elected to a full term in 1942,{{cite news |url=https://news.google.com/newspapers?id=RaZfAAAAIBAJ&pg=2360%2C2654641
Election results ==Family==