1956: Why did so many Western and Midwestern states swing against Ike?

[E-Dawg]

Although Ike did better in the nationwide popular vote in 1956 compared to 1952, most of this was due to gains in the East and South. In the Midwest and West, Eisenhower lost ground to Stevenson in most states, some by significant margins. The states that swung this way were California, Oregon, Washington, Idaho, Montana, Wyoming, Colorado, North Dakota, South Dakota, Nebraska, Kansas, Minnesota, Iowa, and Missouri (which actually flipped from Ike to Stevenson!)  Mississippi and South Carolina in the South did as well, but those are self-explanatory (Dixiecrats who supported Ike in 52 swung against him and to the unpledged ticket due to his pro-civil rights record). What in Ike's presidency caused him to lose ground in such a large part of the country? Did it have anything to do with farm issues? I haven't been able to get an answer for this yet.