Overview
The Opposition Party was a third party in the South in the years just before the American Civil War.
Confusing labels
The late 1850s saw political chaos during the fragmenting of the Second Party System of Jackson Democrats and Clay Whigs. The Democratic efforts to expand slavery into Western territories, particularly Kansas, led to organized political opposition, which coalesced in Congress as the Opposition Party.
As the Whig Party disintegrated, many local and regional parties grew up, some ideological, some geographic. When they realized their numbers in Congress, they began to caucus in the same way American political parties had arisen before the Jacksonian national party conventions. Scholars such as Kenneth C. Martis have adopted a convention to explain the Congressional coordination of anti-Pierce and anti-Buchanan factions as the Opposition Party. The Opposition Party as a third party in the South was made up of political activists who organized, held party conventions and elected members to Congress.
The "Opposition Party" name was adopted by several former Whig politicians in the period 1854–1858. In 1860, the party was encouraged by the remaining Whig leadership to effectively merge with the Constitutional Union Party. The party was seen as offering a compromise position between the Southern Democrats and Northern Republicans.
From Wikipedia (CC BY-SA 4.0).