The Opposition Party was a party identification under which Northern anti-slavery politicians, formerly members of the Democratic and the Whig Parties, briefly ran in the 1850s in response to the expansion of slavery into the new territories. It was one of the movements that arose from the political chaos in the decade before the American Civil War in the wake of the Compromise of 1850. The movement had arisen before and was quickly subsumed by the coalescence of the Republican Party in 1856.