In the late 19th century, most people who lived on the Great Plains were Republicans. This was so for several reasons.

Most of these settlers had migrated to the area from northern states or directly from Europe. They preferred the GOP because they associated the Democratic Party with the South and slavery.

Encouraged by Republican Party leaders, many Americans blamed the Civil War on the Democratic Party’s defense of slavery and slaveholders.

Typically, in the late 19th century, Republican candidates symbolically “waved the bloody shirt” (that is, the shirt of a fallen soldier) by constantly...