In addition to serving during World War II, President Roosevelt was also elected during the Great Depression a few years prior to the war. One of the reasons for his victory was America's distrust in President Hoover, whom they believed did nothing to fix the economy. During his presidency he introduced the set of programs known as the New Deal, which were collectively meant to bring the United States out of the Great Depression. While some of the programs were successful, others were invalidated by the Supreme Court because they violated the Constitution. In addition, Roosevelt upset some with his attempts at restructuring the Supreme Court.
When World War II started, the American people were very clear in their desire to stay out of the conflict in Europe. Nobody wanted to get involved after seeing the losses and devastation caused by World War I. Roosevelt reluctantly fulfilled this wish up until the attack on Pearl Harbor on December 7, 1941.