Perhaps because he was writing in the wake of the Vietnam Era, Schroeder is highly conscious of the 'dammed if you do, damned if you don't' position anti-war politicians often find themselves, when it comes to morally and financially supporting the troops abroad. As was often the case since, most Congressmen, agreed to send aid, even if they opposed the war. But even if congress voted to apportion funds, and obeyed Polk's degree, the dissent to the war continued to be expressed loudly and eloquently by pro-slavery and abolitionist forces alike. For the first time, the oppositional part of the Whigs articulated a clear position against the chief executive's major military policy initiative, creating the foundation, however unintentionally of the modern philosophically differentiated two-party system, where the party out of power often disagrees quite strongly with the foreign policy of the party in power. The notion of how to be a loyal opponent and still show patriotism when the U.S. is fighting a war abroad remains difficult, but the Whigs were able to generate a great deal of support, particularly in New England.

Originally, the Northern Whigs primarily opposed the war because of a fear of adding slave states to the union. However, Southern pro-slavery activists like Senator John Calhoun, also opposed the war in the name of states rights, as he feared the enormous federal and executive powers being commanded by Polk. Diversity amongst religious groups who opposed the war was equally striking, and transcended usual divides between right and left. Although in contemporary politics, liberals and conservatives are usually seen as unified blocks in opposition to or in support of military policies, in Polk's day, conservative Congregationalists and liberal Unitarians both fought against the war. A more substantial coalition was not formed, though, not simply because of the more fractured and spread out

This came to a head during the controversy over the Wilmot Proviso of 1846, which banned slavery in all territories acquired by the war. It further divided the forces rallying against Polk, and although it did not finally pass, may have been the final 'nail' in the coffin between Southerners and Northerners. It also diverted the debate away from the 2 million dollar appropriations of the bill itself, and redirected the debate to the issue of slavery in general.
The "Conscience" versus "Cotton" Whigs or Van Buren vs. Calhoun Democrats, all disliked and opposed the war or one another, or both and Polk's war left American politics less unified than ever, even while the nation grew larger under his leadership. Polk's ambition was vast. According to Schroder, Polk only reluctantly signed the Treaty of Guadalupe Hidalgo of 1848, bringing the war to a close. He dreamed of adding all of Mexico to the U.S., drunk on his own power and a vision of a newly expansionist American foreign policy. The ultimate settlement conferred what would become new states of California and New Mexico for $15 million, but along with this apparent gain was a great loss, the loss of any hope of reconciliation between the states without war. Regardless of whether one agrees with the author's thesis about the seismic impact of the Mexican-American war on subsequent tensions between pro-slavery and anti-slavery factions, the story Schroder tells is a potent illustration that it is not enough merely to oppose something unpopular, rather some common ideal must unite the opposition for it to be effective against a powerful regime, lead by a man like Mr. Polk.