In the mid-1970s, because of his work exploring the Truman and Eisenhower loyalty and security programs as well as his articles on FBI wiretapping, Theoharis was asked by the Church Committee to conduct research at presidential libraries. The Church Committee - the Senate select committee to study governmental operations with respect to intelligence activities - was formed by Senator Frank Church after Nixon administration, FBI, and CIA abuses became public. First without and then with qualified security clearances, Theoharis examined some presidential records relating to the FBI and White House at the Eisenhower, Kennedy, and Johnson presidential libraries. He also examined some FBI records for the Church Committee at FBI headquarters.