It's said to be the most famous political ad of all time, perhaps on a par with the "Mean Joe Green" Pepsi ad.
I well remember seeing it at the time, and thinking then that this was LBJ's excuse for not winning in Vietnam.
Events of the following four years bore that out, though it took until 1975 for the final humiliations: 
gleeaikin: "If what I saw about certain Texas companies and the Texas Book Repository Bldg. plus some things I heard this evening about the Warren Commission report on the assassination are true, then the only thing that mattered was that Johnson become president, and keep the MIC money flowing into Texas."
Over the years since October 1963 I've seen many conspiracy theories come a go regarding the Kennedy assassination, and I've never been interested enough to spend the time necessary to learn all the facts needed to judge which theories are more likely right than wrong.
I was most curious to hear RFK, Jr. recently claim it was the CIA which arranged his uncle's murder, something to do with the Bay of Pigs, though I didn't catch the connection.
So, if I were to rank the Top Ten conspiracy theories on JFK's assassination, then RFK, Jr.'s ideas would be up there somewhere near the top.