A member of the Democratic Party, he was Commissioner of the U.S. Bureau of Indian Affairs (1961–1966) during the presidencies of John F. Kennedy and Lyndon B. Johnson.

Earlier in his career, he served more than 10 years as a political appointee in the Franklin D. Roosevelt and Harry S. Truman administrations, including as Special Assistant directly to President Harry S. Truman (1946–1952), influencing his policy on desegregation of the armed forces and federal government, as well as policy related to Native Americans and other minorities.

[1] Nash worked on Truman's initiatives related to civil rights, including advising him of how to proceed with integration of the United States Armed Forces during a several-year period.

The same day, he issued Executive Order 9980 to end racial discrimination in hiring in the federal government and initiate desegregation in the workplace (which President Woodrow Wilson had segregated in 1914).

[4] From 1961–1966, Nash returned to Washington, D.C., from Wisconsin, where he was appointed as Commissioner of the United States Bureau of Indian Affairs during the administrations of John F. Kennedy, and Lyndon B. Johnson.

[5] He returned to Washington, D.C., from 1961–1966, heading the Bureau of Indian Affairs, during a period when Native Americans were pressing for social justice.