I ran across this yesterday in a book I was reading. From spring 1940:

“Sentiment for going to war with Germany has increased since the Nazi invasion,” Dr. George Gallup, the nation’s best-known pollster, wrote while British warships were still ferrying retreating Allied troops off the Continent, “but the increase has been less than four percent. A nation-wide survey just completed finds the country still more than 13 to 1 against American entrance into the conflict.”