declaration of war against Mexico and also pushed through the restoration of the Independent Treasury System and a bill that reduced tariffs; opposition to the passage of these Democratic policies helped to reunify and reinvigorate the Whigs. In August 1846, Polk asked Congress to appropriate $2 million in hopes of using that money as a down payment for the purchase of California in a treaty with Mexico. Democratic Congressman David Wilmot of Pennsylvania offered an amendment known as the Wilmot Proviso, which would ban slavery in any newly acquired lands. The Wilmot Proviso passed the House with the support of both Northern Whigs and Northern Democrats, breaking the normal pattern of partisan division in congressional votes, but it was defeated in the Senate. Nonetheless, clear divisions remained between the two parties on territorial acquisitions, as most Democrats joined Polk in seeking to acquire vast tracts of land from Mexico, but most Whigs opposed territorial growth. In February 1848, Mexican and U.S. negotiators reached the Treaty of Guadalupe Hidalgo, which provided for the cession of Alta California and New Mexico. Despite Whig objections to the acquisition of Mexican territory, the treaty was ratified with the support of a majority of the Democratic and Whig senators; Whigs voted for the treaty largely because ratification brought the war to an immediate end. During the war, Whig leaders like John J. Crittenden of Kentucky began to look to General Taylor as a presidential candidate in the hopes that the party could run on Taylor's personal popularity rather than economic issues. Taylor's candidacy faced significant resistance in the Whig Party due to his lack of public commitment to Whig policies and his association with the Mexican–American War. In late 1847, Clay emerged as Taylor's main opponent for the Whig nomination, appealing especially to Northern Whigs with his opposition to the war and the acquisition of new territory. With strong backing from slave state delegates, Taylor won the presidential nomination on the fourth ballot of the 1848 Whig National Convention. For vice president, the Whigs nominated Millard Fillmore of New York, a pro-Clay Northerner. Anti-slavery Northern Whigs disaffected with Taylor joined with Democratic supporters of Martin Van Buren and some members of the Liberty Party to found the new Free Soil Party; the party nominated a ticket of Van Buren and Whig Charles Francis Adams Sr. and campaigned against the spread of slavery into the territories.