While there were many war hawks who greatly favored going to war with Mexico, there were also many in the United States who vehemently opposed it. Most of the opposition came from the northern states. There were abolitionists who worried that newly captured territory could be used to expand slavery, which would greatly upset the finely tuned balance between free states and slaveholding states in the country. In an attempt to diffuse this standoff, Pennsylvania Democratic Congressman David Wilmot proposed a proviso which would prohibit slavery in any captured territory. When this proviso failed to pass the Senate, opposition to the war ramped up.
There was also political opposition to going to war. Many members of the Northern Whig and Liberty Parties felt that this war would greatly elevate the position and clout of President James Polk, a Democrat. On the other hand, most Democrats in Congress seemed to be in favor of the war.
Still, others opposed the war because they saw it as an...
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