Polk, anticipating victory and Mexico’s consequent cession…

Polk, anticipating victory and Mexico’s consequent cession of territory, has asked congress for two million dollars to facilitate negotiations.

The war is a partisan issue in the United States, increasingly divided by sectional rivalry, an is essential element in the origins of the American Civil War.

Most Whigs in the North and South oppose it; most Democrats support it.

Southern Democrats, animated by a popular belief in Manifest Destiny, support it in hope of adding slave-owning territory to the South and avoiding being outnumbered by the faster-growing North.

Northern antislavery elements fear the expansion of the Southern Slave Power; Whigs generally want to strengthen the economy with industrialization, not expand it with more land.

Among the most vocal opposing the war in the House of Representatives is John Quincy Adams of Massachusetts.

Adams had first voiced concerns about expanding into Mexican territory in 1836 when he opposed Texas annexation.

He continues this argument in 1846 for the same reason.

War with Mexico will add new slavery territory to the nation.

When the vote to go to war with Mexico came to a vote on May 13, Adams had spoken a resounding "No!" in the chamber.

Only thirteen others had followed his lead.

Ex-slave Frederick Douglass opposes the war and is dismayed by the weakness of the anti-war movement.

Democrats want more land; northern Democrats are attracted by the possibilities in the far northwest.

Joshua Giddings, who leads a group of dissenters in Washington D.C., calls the war with Mexico "an aggressive, unholy, and unjust war", and votes against supplying soldiers and weapons. 

Fellow Whig Abraham Lincoln contests Polk's causes for the war.

Polk had said that Mexico had "shed American blood upon American soil".

Lincoln submits eight "Spot Resolutions", demanding that Polk state the exact spot where Thornton had been attacked and American blood shed, and clarify whether or not that location was actually American soil, or in fact had been claimed by Spain and Mexico.

Whig Senator Thomas Corwin of Ohio gives  a long speech indicting presidential war in 1847. 

Northern abolitionists attack the war as an attempt by slave-owners to strengthen the grip of slavery and thus ensure their continued influence in the federal government.

Prominent artists and writers oppose the war.

The Transcendentalist writers Henry David Thoreau and Ralph Waldo Emerson attack the popular war.

Thoreau, whoserves jail time for his opposition, will turn a lecture into an essay now known as Civil Disobedience.

Emerson is succinct, predicting that, "The United States will conquer Mexico, but it will be as a man who swallowed the arsenic which brings him down in turn. Mexico will poison us."

Events will prove him right, as arguments over the expansion of slavery in the lands seized from Mexico will fuel the drift to civil war just a dozen years later.

Democratic Representative David Wilmot introduces the Wilmot Proviso, which would prohibit slavery in new territory acquired from Mexico.

The House passes the amended bill on August 8, 1846, but it dies in the Senate, spurring further hostility between the factions.