Despite the Whig victory in 1840, planters wielded considerable clout in Washington, D.C., because of the importance of cotton to the U.S. economy. In turn, Southerners needed federal support to expand into more fertile areas. The presidential election of 1844 turned on this issue, with Democratic candidate James K. Polk demanding continued expansion into Oregon and Mexico. Once Polk was in office, his claims were contested not only by Britain and Mexico but also by the Comanche. After the United States won vast Mexican territories in 1848, conflicts with Indians and debates over slavery only intensified.