The resolutions were not incidental to US politics. The practice of instructing senators was taken up by the antislavery movement beginning in the crisis over the admission of Missouri as a slave state in 1821. Northern state legislatures intervened with resolutions in the 1830s instructing members of the Senate as well as the House of Representatives to protest the gag rule by which the southern congressional leaders suppressed antislavery petitions. On the other side, slave states passed resolutions condemning abolitionists and favoring suppression of antislavery literature. After the Mexican War, northern states passed resolutions urging the prohibition of slavery in the territories through a measure called the Wilmot Proviso, which never passed. Congressman Abraham Lincoln voted in favor of it numerous times and declared himself a “Proviso Man”. That idea became the central platform of the new Republican party on which Lincoln was elected in 1860.