1968 and 1972 primaries were sh**tshows for the Democratic Party, and lucky for Republicans, so were all of the rest of them until the 90s. There was really a 20 year dominance by the Republicans at the presidential level - the candidates for the Democrats were kinda like Joe - just bland (easily portrayed as weak) liberal white men up against much more superior conservative candidates.
The Nixon ads in '68 and '72 were also some of the best ever made.
http://www.livingroomcandidate.org/commercials/1972