"By 1980, the farm vote had turned almost solid Red." "Reagan received 62% of the farm vote." Did you forget Carter's cut to subsidies, his embargoes, soil unpopular conservation policies? perhaps you should not rely on anecdotal evidence & personal, bias memory.
Here is 1988. Dukakis won big in many farm counties. Carter won my home farm township 2:1 in 1980. The farm world is not all the same. My ancestors were active in the leftie Farmer Labor Party in the 1930s. fDR wasn’t left enough. FL ran Minnesota in the 1930s
In the 1980 election the farm crisis wasn't in full swing yet.