The ideology of the Repeblican party has not changed much over the decades. It has since 1865 been the party of the white Christian, originally protestant, minority. While the  Democrats became an alliance of the southern, anti northern people and the minorities, mostly Catholic, unified only by their resentment of the majority. The famous description of the Democrat party in 1888 as "rum, Romanism, and rebellion"was largely true. The Republicans were pro business all through those decades when the US became the richest , most innovative country in history. It is the Democrats who have developed the ideology which divides the country, becoming pro abortion, the biggest single divider. But the democrats became anti business, anti majority, anti assimilation,pro immigration, and more recently, anti Christian. The have promoted division as a calculated political strategy. Divide and conquer. 
The Midwest has historically been  Republican, far longer than the south.