Commercial - Humphrey 1968 Election Ad ( Laughing at Spiro T.Agnew )

Attack ads didn't start in the 1990s.  This ad is what looks like a rather clumsy attack on Richard Nixon's running mate Spiro Agnew, at that time, unknown on the national scene.  I remember little about the context of the ad, if it was based on Agnew's name or him being unknown.  This was brought up on last Wednesday's Rachel Maddow Show.