 The Massachusetts Democratic Party was highly factionalized, which contributed to Morton's long string of defeats. His brief periods of ascendancy, however, resulted in no substantive Democratic-supported reforms, since the dominant Whigs reversed most of the changes enacted during his terms. An opponent of the extension of slavery, he split with longtime friend John C. Calhoun over that issue, and eventually left the party for the Free Soil movement. He was considered by Martin Van Buren as a potential vice presidential running mate in 1848.
