The west Mississippi River states were all carried by Clinton TWICE. He easily carried Missouri, Arkansas, and Louisiana, states that weren't in play in 2000 or 2004.
He of course carried Arkansas because it was his home state. Missouri was relatively close in 2000. Louisiana was 52% for Clinton in 1996, which really surprises me since it's so socially conservative and wasn't even close in 2000 or 2004.
What exactly makes these neighboring columns of states so different? If Arkansas and Louisiana are THAT socially conservative, what keeps them from being as heavily Republican as the states to the west?
Higher black population. (Many socially conservative blacks vote Democrat.)