with the Preemption Act of 1841. 1844 presidential election President Tyler's break with the Whig Party, combined with Webster's continuing affiliation with Tyler, positioned Clay as the leading contender for the Whig nomination in the 1844 presidential election. By 1842, most observers believed that Clay would face Van Buren in the 1844 presidential election, as he had still remained as the clear leader of the Democrats and, following the tradition of the founders, wanted a second term. Hoping to win another term, President Tyler forged an alliance with John C. Calhoun and pursued the annexation of the Republic of Texas, which would add another slave state to the union. After President Tyler concluded an annexation treaty with Texas, Clay announced his opposition to annexation. He argued that the country needed "union, peace, and patience," and annexation would bring tensions over slavery and war with Mexico. The same day that Clay published a letter opposing the annexation of Texas, Van Buren also came out against annexation, citing similar reasons as Clay, so that slavery and especially expansionism seemed to play no role in the next election. Clay unanimously won the presidential nomination at the 1844 Whig National Convention, but a minority of expansionist Southern Democrats, encouraged by Tyler's alternative outline, blocked Van Buren's nomination at the 1844 Democratic National Convention for countless ballots, until Van Buren withdrew, making place for an unexpected compromise candidate: The party nominated former Speaker of the House James K. Polk of Tennessee, who favored annexation, but in order to calm anti-expansionists, promised to just run for a single term. Following the nomination of a pro-annexation Democrat, Tyler soon ended his incipient independent run for president and endorsed Polk. Clay was surprised by Van Buren's defeat but remained confident of his chances in the 1844 election. Polk was the first "dark horse" presidential nominee in U.S. history, and Whigs mocked him as a "fourth rate politician." Despite his relative lack of national stature, Polk proved to be a strong candidate capable of uniting the factions of the Democratic Party and winning the support of Southerners who had been reluctant to support Van Buren. Clay's stance on slavery alienated some voters in both the North and the South. Pro-slavery Southerners flocked to Polk, while many Northern abolitionists, who tended to align with the Whig Party, favored James G. Birney of the Liberty Party. Clay's opposition to annexation damaged