What two groups were against the Mexican American war and why?

Two prominent groups that opposed the Mexican-American War were the Whig Party and various abolitionist organizations. The Whig Party argued that the war was driven by a desire for territorial expansion and was morally unjust, fearing it would extend slavery into new territories. Abolitionists opposed the war because they believed it would lead to the spread of slavery, undermining their efforts to abolish it altogether and promoting an agenda that favored slaveholding interests.