The Whig Party convinced the reluctant Taylor to lead their ticket in the 1848 presidential election, despite his unclear political tenets and lack of interest in politics. At the 1848 Whig National Convention, Taylor defeated Scott and former Senator Henry Clay to take the nomination. He won the general election alongside New York politician Millard Fillmore, defeating Democratic Party candidates Lewis Cass and William Orlando Butler, as well as a third-party effort led by former president Martin Van Buren and Charles Francis Adams, Sr. of the Free Soil Party. Taylor became the first president to be elected without having served in a prior political office. Taylor became the first president to be elected without having served in a prior political office. As Taylor took office, Congress faced a battery of questions related to the Mexican Cession, acquired by the U.S. after the Mexican War and divided into military districts. It was unclear which districts would be established into states and which would become federal territories, while the question of their slave status threatened to bitterly divide Congress.