It's easy to defend this statement, particularly in economic terms. Looking at one example from each administration:
- During Harding's administration, Secretary of the Treasury Andrew Mellon instituted many conservative policies. For he reduced taxes, mainly on the rich and he balanced the federal budget.
- Coolidge is famous for saying that "the chief business of the American people is business." His Secretary of Commerce, Herbert Hoover, worked with businesses to create trade associations to allow businesses in a given industry to work together to create greater efficiency.
- As president, Hoover is, of course, famous for being very reluctant to spend government money on trying to get the country out of the Depression.
These are all conservative actions taken by presidents during the 1920s.