Remember the "Daisy Girl" spot?

Perhaps the most famous presidential campaign commercial in history was the one for Lyndon Johnson in 1964 in which the not-so-subtle message was that Republican challenger Barry Goldwater might start a nuclear war.

The "Daisy Girl" ad, as it was known, aired only once -- on NBC, during the movie "David and Bathsheba" on Sept. 7 of that year. But countless millions of Americans have seen it in documentaries and news reports over the past 43 years.