During World War II there were two sides: the Allies, which the US were a part of, which included, among others, UK, France, Soviet Union (after 1941), and the allies (Germany, Japan, Italy and their puppet states).
So the answer can be any of the allies: UK, France, Soviet Union but also the whole of Latin America, most of Africa and Asia.
The most important political leaders during this time were Theodore Roosevelt, Robert M. La Follette, Charles Evans Hughes, and Herbert Hoover. Some democratic leaders included William Jennings Bryan, Woodrow Wilson, and Al Smith. This movement targeted the regulations of huge monopolies and corporations.
Harrison was the first president to campaign actively for office, he wrote the slogan "Tippecanoe and Tyler too"
