There was, and it was led by the Left, and they continued to agitate even after the war started. The Left suddenly became hawks when Hitler attacked former ally, the USSR.
The "antiwar" movement pre-WWII was in fact mostly populated by conservatives -- just look up the history of the "America Firsters". The interventionists were more likely to be allied with FDR. Similar with WWI, Wilson was eager to jump in, most Republicans were not (except for T. Roosevelt, who was pretty anomalous among Republicans back then).
The far-lefties back in the 1930s were, starting with the Spanish Civil War, very enthusiastic about fighting Germany, Italy and Franco -- basically because they were viewed as a threat to Communism.