Despite Taylor's unclear political affiliations and beliefs, and the Whig opposition to the Mexican-American War, the 1848 Whig National Convention nominated the popular general over party stalwarts such as Henry Clay and Daniel Webster. For vice president, the Whigs nominated Millard Fillmore, a New York Whig known for his moderate views on slavery. Incumbent President James K. Polk, a Democrat, honored his promise not to seek re-election, leaving his party's nomination open. The 1848 Democratic National Convention rejected former President Martin Van Buren's bid for a second term, instead nominating Senator Lewis Cass of Michigan. Van Buren broke from his party to lead the ticket of the Free Soil Party, which opposed to the extension of slavery into the territories.

Answer this question based on the passage: whom did the free-soil party nominate as its presidential candidate in 1848? OK. Let's think. My stream of consciousness:
The important part for answering this question is: Van Buren broke from his party to lead the ticket of the Free Soil Party, which opposed to the extension of slavery into the territories. The answer is Martin Van Buren.