Brilliant article on this here:
Steve Cone: The Big Bang of Attack Ads
The spot starts with a little girl picking daisies in a meadow and counting aloud as she plucks each petal. She mixes up her numbers, which brilliantly reinforces the innocence of a small child. Then a man's voice is heard counting down from ten. It's official sounding -- like something right out of the Pentagon War Room. As the countdown proceeds the camera zooms in on the little girl's face, and then her eye and finally from her eye the image of an atomic blast appears and fills the screen. Next you heard President Johnson quote several lines taken form a W.H. Auden poem about how "we must love each other or surely we will die." And finally a professional voice over announces to vote for President Johnson on November 3rd. "The stakes are too high to do anything else."