After leaving office as territorial delegate, McCormick become a commissioner of the Centennial Exposition. This was followed by becoming secretary of the Republican National Committee in August 1876 and his working in the U.S. presidential campaign of Rutherford B. Hayes. In 1877, McCormick was appointed Assistant Secretary of the Treasury. This was followed by his being named United States Commissioner General to the Paris Exposition in November 1877. At the end of his service as commissioner, he was appointed Commander, Legion of Honor, by the President of France in 1878.