Public opinion on entering the war became polarized in very complicated ways. Conservatives divided into pro-war ("interventionist") and anti-war ("isolationist") blocs, as did liberals. Republicans split and Democrats split. FDR was the leader of the interventionist liberal Democrats, but he was opposed by old allies like [[John L. Lewis]] and [[Joe Kennedy]], and supported by old foes like [[Henry Stimson]].
In general the dispute was entirely focused on Europe. Virtually every group was hostile to Japan and supported a strong pro-[[Nationalist China]] policy, which FDR pushed vigorously. Tokyo was threatened: end its invasion of China or FDR would--and did at urging of [[KGB]] agent [[Harry Dexter White]] working as an Undersecretary of the Treasury--cut off Japan's oil supplies. Japan responded to an ultimatum--written by Harry White--with a decision for war. Once Pearl Harbor was attacked (Dec. 7, 1941), all the prior divisions vanished overnight, and all groups supported the war effort. Later stories to the effect that FDR knew about the Pearl Harbor attack in advance were all false fabrications.
see [[American Homefront, World War II]]