As a Senator, Douglas was a leading liberal. He fought for civil rights before it was fashionable. He was an advocate for public housing and opposed real estate redlining. A fateful compromise of Douglas' was his acceptance in 1949 of a provision in a public housing bill making it difficult for suburbs to build low-income housing (not that they ever wanted to).
Douglas lost re-election in 1966 to Charles Percy.
Prior to his political career, Douglas helped develop the Cobb-Douglas functional form, often used for production functions in economics.