Black Republicans was a derogatory term used by Democrats against members of the Republican Party who were accused of supporting Black emancipation. The term was used to try to play on public racism and undermine Republican candidates.

Referring to a dye from the butternut tree used to color clothes, Butternuts were settlers in the southern regions of the free states of Ohio, Indiana, and Illinois who reliably voted for Democrats in contrast to the usually pro-Republican North. They were a major source of support for Peace Democrats in the North.

Also known as the Peace Democrats, Copperheads were Democrats during the Civil War who advocated for an immediate peace with the Confederacy, even if it meant recognizing the Confederacy as an independent nation. They were a major source of opposition to the Lincoln administration during the Civil War.

In the South, fire-eaters were Southern politicians who strongly supported immediate secession from the United States.

Free soil was a general term for politicians and advocates who shared opposition to the expansion of enslavement. The free soil movement would give rise to the Republican Party.

Habeas corpus is a Latin term referring to the constitutional power of courts to review and challenge the imprisonment of an individual by authorities. In both the Union and the Confederacy during the Civil War, the right of individuals to habeas corpus was suspended, arousing anger and controversy.