According to Wikipedia:
Though only aired once (by the campaign), it is considered an important factor in Johnson's landslide victory over Barry Goldwater and an important turning point in political and advertising history.
The Tagline was:
These are the stakes. To make a world in which all of God's children can live, or to go into the dark. We must either love each other, or we must die.
I wonder whether an ad like that would have the same impact in today's world.
Just for the record, the ad was remade in 2010 (but I don't feel that it has the same impact)
There is also a 2 second reference to it in the Simpson's episode "Sideshow Bob's Last Gleaming" (and 17:01) but I can't find a clip of those few seconds to place here. You'll have to believe me that it shows Lisa pulling the petals off a daisy, then a close up of the pupil of her eye. Then a nuclear explosion.