Complex sentence: The first was a return to isolationism, minimizing American involvement with the rest of the world, a policy that was supported by conservative Republicans, especially from the Midwest, including former President Herbert Hoover and Senator Robert A. Taft.
Split into simpler sentences: The first was a return to isolationism, minimizing American involvement with the rest of the world. This policy was supported by conservative Republicans, especially from the Midwest, including former President Herbert Hoover and Senator Robert A. Taft.