After mid-1841, congressional Whigs continually pressured Webster to resign, and by early 1843, Tyler had also begun to pressure Webster to leave office. As Tyler moved even farther away from Whig positions and began preparing a campaign for the Democratic nomination in the 1844 United States presidential election, Webster left office in May 1843. With Webster gone, Tyler turned his attention to the annexation of the Republic of Texas. Clay was nominated for president at the 1844 Whig National Convention, while the Democrats spurned both Tyler and former President Van Buren in favor of James K. Polk, a protege of Andrew Jackson. Webster's service in the Tyler administration had badly damaged his credibility among Whigs, but he began to rebuild old alliances within the party. Tyler's attempts to annex Texas became the key issue in the 1844 election, and Webster came out strongly against annexation. He campaigned on behalf of Clay, telling one crowd, "I know of no great national constitutional question; I know of no great interest of the country ... in which there is any difference between the distinguished leader of the Whig Party and myself." Despite Webster's campaigning, Polk defeated Clay in a close election. The election of the expansionist Polk ensured the annexation of Texas, and annexation was completed after Polk took office.