FD Roosevelt was the first President to seek a third term (and subsequently a fourth term too) in the history of America. This was unprecedented and even his party members were not supportive. To increase his chances of winning, he tried to appease the American people by declaring publicly that he would not support the war. But that was all a lie. He jumped onto the opportunity to declare war immediately when Pearl Harbour was attacked.
http://wherebearsroamfree.blogspot.sg/2013/08/american-liberty-how-ww2-boosted.html