The WA list is interesting. I didn't know that Dukakis had picked up those rural counties. Clark and Whatcom can easily be explained, though (the former due to suburban/exurban growth, the latter due to Nader).
Dukakis actually overperformed in rural areas because farmers got hit pretty hard economically during the Reagan presidency. It's why he won Iowa and West Virginia and did much better in Missouri, Kansas, South Dakota, and Montana, than his overall national performance.
You're right about the farm vote except in WV which has almost no large scale agriculture because it's all mountains.
