The U.S. Federal Government is the world's largest research organization. Here are some tools which can be used to find Federal Government research on Presidential polciies, actions, etc.
Federal Government Oversight Agencies
Congressional Research Service, Congressional Budget Office, and General Accountancy Office are excellent sources of expert and non-partisan studies of government.
Access to nearly every document created by Congress, including committee hearings.
Catalog of U.S. Government Publications
General-purpose finding tool for publications from a wide range of agencies.
You have access to various collections of official U.S. Presidential documents.