Answer:
- Whig party
- Free Soil party
Step-by-step explanation:
The Whig party was the main precursor to the Republican party. They were very influential in the U.S. before the Civil War and if not for sectional divisions, would have contributed a slew of Presidents. The Whig party wasn't a big opponent of slavery but the Northern Whigs felt strongly enough against it to switch to the Republican party in the decade before the Civil War.
There was also the Free Soil party. This party was dedicated to ensuring that slavery would not spread to the new territories that the U.S. had acquired. They found it beneficial to join the Republican party which was anti-slavery.