SECTIONAL CONFLICT AND CRISIS, 1844–1861A Divisive War, 1844–1850The U.S.-Mexico War roused bitter sectional conflict. Northern Whigs, or conscience Whigs, opposed the war on moral grounds and accused Polk of waging the war to add new slave states and increase slave owning Democrats’ control of the federal government. Whigs gained control of Congress through the 1846 election. Antislavery Democrats supported the Wilmot Proviso (1846), a plan intended to prohibit slavery in any new territories acquired from Mexico; the Senate killed the proviso. “Conscience Whigs” viewed the U.S.-Mexico War as a conspiracy to add new slave states in the West. To reunite Democrats before the election, Polk and Buchanan abandoned their expansionist hopes for Mexico and agreed to take only California and New Mexico. In the Treaty of Guadalupe Hidalgo (1848), the United States agreed to pay Mexico $15 million for Texas north of the Rio Grande, New Mexico, and California. The establishment of the Oregon Territory and the acquisition of New Mexico and California in 1848 seemed to have fulfilled Manifest Destiny. Debates over expansion dominated the election of 1848. The Senate’srejection of the Wilmot Proviso revived charges that southern politicians were leading a “slave power” conspiracy to dominate the federal government. The Free Soil Party, organized in 1848, viewed slavery as a threat to republicanism and to the Jeffersonian ideal of a freeholder society (and not, as the Liberty Party believed, a sin against the natural rights of African Americans).