[1] Robinson was a member of the Indiana Senate from 1914 to 1918, he and was the Republican floor leader during the entire period.

He resumed the practice of law and was judge of Marion County Superior Court in 1921–1922.

He resumed the practice of law in Indianapolis, in 1922 and was appointed on October 20, 1925, to the U.S. Senate by Governor Edward L. Jackson and subsequently elected on November 2, 1926, in the 1926 United States Senate special election, to fill the vacancy caused by the death of Samuel M. Ralston.

While in the Senate he was chairman of the Committee on Pensions (Seventieth through Seventy-second Congresses).

He became a 33° Scottish Rite Mason in the Valley of Indianapolis in 1924 and served on the Supreme Council of DeMolay between 1925 and 1927.