The Four Factions of Lincoln’s Era: The Whig/Republicans, the “Know-Nothing” Constitutional Union, the Southern Democrats, and the Free Soil Party
This will make more sense if we consider the four factions of Lincoln’s era explicitly, they were:
The Northern liberal Whig/Republicans,
The Nativist Know-Nothing [sometimes] allies of the Whig/Republicans,
The Southern Democrats and their Northern allies (who supported slavery), and
The Free Soil [sometimes] allies of the Democrats who took a “libertarian” like position.