テキサス併合
Tyler submitted his Texas-US treaty for annexation to the US Senate, delivered April 22, 1844, where a two-thirds majority was required for ratification. The newly appointed Secretary of State John C. Calhoun of South Carolina (assuming his post March 29, 1844) included a document known as the Packenham Letter with the Tyler bill that was calculated to inject a sense of crisis in Southern Democrats of the Deep South. In it, he characterized slavery as a social blessing and the acquisition of Texas as an emergency measure necessary to safeguard the "peculiar institution" in the United States. In doing so, Tyler and Calhoun sought to unite the South in a crusade that would present the North with an ultimatum: support Texas annexation or lose the South. Anti-slavery Whigs considered Texas annexation particularly egregious, since Mexico had outlawed slavery in Coahuila y Tejas in 1829, before Texas independence had been declared.