In negotiating Tyler-Upshur`s secret annexation with Texas near the penitentiary period, Senator Robert J. Walker of Mississippi, a key ally of Tyler,`s, published a widely circulated and influential letter, reproduced as a pamphlet and advocating for immediate annexation.  In this paper, Walker argued that Texas could be acquired by Congress in different ways, all constitutionally, and that moral authority was based on the rules of territorial expansion established by Jefferson and Madison, and had been proclaimed as doctrine by Monroe in 1823.  Senator Walker`s polemic offered an analysis of Texas` importance to slavery and race. It presented itself in Texas as a corridor that would “defame” free and enslaved African Americans in a gradual exodus southward, which would eventually provide labour goods to the Central American tropics and, over time, free the United States from its slave population.  When President Polk took office on March 4 (at noon), he was able to recall Tyler`s shipment to Texas and reverse his decision. On March 10, after consulting with his firm, Polk confirmed Tyler`s approach and allowed the courier to travel to Texas with the immediate annexation offer.  The only change was to excite the Texans, to unconditionally accept the conditions of annexation.  Polk`s decision was based on his concern that a lengthy negotiation by the American commissioners would reveal efforts to annex foreign intrigue and interference.  While Polk secretly guarded his annexation efforts, senators passed a resolution calling for the formal disclosure of the government`s Texas policy. Polk stopped and, when the special session of the Senate was postponed on March 20, 1845, he had not submitted names for the American commissioners in Texas.
Polk rejected Senator Benton`s accusations that he had misled Benton about his intention to support the new bargaining option and said, “If such commitments were made, it was in a complete misunderstanding of what I said or meant.”  Tyler presented his annexation treaty to the Senate, introduced on April 22, 1844, where a two-thirds majority was required for ratification.   Foreign Minister Calhoun (in accepting his mandate on 29 March 1844)  had sent a letter to British Minister Richard Packenham denouncing the interference of British anti-slavery in Texas. He included Packenham`s letter with the Tyler Act, with the goal of creating a sense of crisis among Southern Democrats.  He called slavery a social blessing and the acquisition of Texas as a necessary emergency measure to protect the “peculiar institution” in the United States.  Tyler and Calhoun thus attempted to unite the South in a crusade that provided an ultimatum to the North: support for the annexation of Texas or loss of the South.  In July 1845 Polk, elected on an expansionist platform, ordered the commander of the U.S. Army in Texas, Zachary Taylor, to transfer his troops to the disputed countries between the Nueces and Rio Grande rivers. In November, Polk sent Congressman John Slidell to Mexico with orders to negotiate the purchase of disputed areas along the Texas-Mexico border and the territory of the present-day states of New Mexico and California.