C- Mr Polk's War
Opposition to the Mexican-American War was primarily led by members of the Whig Party, who referred to it as "Mr. Polk's War." President James K. Polk had initiated the conflict in 1846 by ordering U.S. troops to cross the Rio Grande into what was then Mexican territory. The Whigs opposed the war on several grounds, including concerns over the morality of taking land from a neighboring country and the fear that the expansion of slavery into new territories acquired from Mexico would upset the balance of power between free and slave states. The war ultimately resulted in a U.S. victory, with Mexico ceding a significant portion of its territory to the United States in the Treaty of Guadalupe Hidalgo.