Led by John Van Buren, the Barnburners bolted from the 1848 Democratic National Convention after the party nominated a ticket consisting of Senator Lewis Cass of Michigan and former Congressman William O. Butler of Kentucky; Cass and Butler had both opposed the Wilmot Proviso.
Shortly after the Democrats nominated Cass, a group of Whigs made plans for a convention of anti-slavery politicians and activists in the event that the 1848 Whig National Convention nominated General Zachary Taylor of Louisiana for president.
With the strong backing of slave state delegates, Taylor defeated Henry Clay to win the Whig presidential nomination.
For vice president, the Whigs nominated Millard Fillmore of New York, a conservative Northerner.
The nomination of Taylor, a slaveholder without any history in the Whig Party, spurred anti-slavery Whigs to go through with their convention, which would meet in Buffalo, New York in August.
A faction of the Liberty Party led by Salmon P. Chase agreed to attend the convention, though another faction of the party, led by Gerrit Smith, refused to consider merging with another party.

Meanwhile, Barnburners convened in Utica, New York on June 22; they were joined by a smaller number of Whigs and Democrats from outside New York.
Though initially reluctant to accept to run for president, former President Van Buren accepted the group's presidential nomination.
Van Buren endorsed the position that slavery should be excluded from the territories acquired from Mexico, further declaring his belief that slavery was inconsistent with the "principles of the Revolution".
Because Van Buren had favored the gag rule and had generally accommodated pro-slavery leaders during his presidency, many Liberty Party leaders and anti-slavery Whigs were unconvinced as to the sincerity of Van Buren's anti-slavery beliefs.
Historian A. James Reichley writes that, while resentment stemming from his defeat at the 1844 Democratic National Convention may have played a role in his candidacy, Van Buren ran on the grounds that "the long-term welfare of [the Democratic Party], and the nation, required that the [Democratic Party] shed its Calhounite influence, even at the cost of losing an election or two."

With mix of Democratic, Whig, and Liberty Party attendees, the National Free Soil Convention convened in Buffalo early August.
Anti-slavery leaders made up a majority of the attendees, but the convention also attracted some Democrats and Whigs who were indifferent on the issue of slavery but disliked the nominee of their respective party.
Salmon Chase, Preston King, and Benjamin Franklin Butler led the drafting of a platform that not only endorsed the Wilmot Proviso but also called for the abolition of slavery in Washington, D.C. and all U.S. territories.
With the backing of most Democratic delegates, about half of the Whig delegates, and a small number of Liberty Party leaders, Van Buren defeated John P. Hale to win the fledgling party's presidential nomination.
For vice president, the Free Soil Party nominated Charles Francis Adams Sr.,
the youngest son of the recently-deceased John Quincy Adams.

Some Free Soil leaders were initially optimistic that Van Buren could carry a handful of Northern states and force a contingent election in the House of Representatives, but Van Buren did not win a single electoral vote.
However, the nomination of Van Buren alienated many Whigs; except in northern Ohio, most Whig leaders and newspapers rallied around Taylor's candidacy.
Ultimately, Taylor won the election with a majority of the electoral vote and a plurality of the popular vote, improving on Clay's 1844 performance in the South and benefiting from the defection of many Democrats to Van Buren in the North.
Van Buren won ten percent of the national popular vote and fifteen percent of the popular vote in the Northern states; he received a popular vote total five times greater than that of Birney's 1844 candidacy.
Van Buren was the first third party candidate in U.S. history to win at least ten percent of the national popular vote.
In concurr
Led by John Van Buren, the Barnburners bolted from the 1848 Democratic National Convention after the party nominated a ticket consisting of Senator Lewis Cass of Michigan and former Congressman William O. Butler of Kentucky; Cass and Butler had both opposed the Wilmot Proviso. Shortly after the Democrats nominated Cass, a group of Whigs made plans for a convention of anti-slavery politicians and activists in the event that the 1848 Whig National Convention nominated General Zachary Taylor of Louisiana for president. With the strong backing of slave state delegates, Taylor defeated Henry Clay to win the Whig presidential nomination. For vice president, the Whigs nominated Millard Fillmore of New York, a conservative Northerner. The nomination of Taylor, a slaveholder without any history in the Whig Party, spurred anti-slavery Whigs to go through with their convention, which would meet in Buffalo, New York in August. A faction of the Liberty Party led by Salmon P. Chase agreed to attend the convention, though another faction of the party, led by Gerrit Smith, refused to consider merging with another party.
Meanwhile, Barnburners convened in Utica, New York on June 22; they were joined by a smaller number of Whigs and Democrats from outside New York. Though initially reluctant to accept to run for president, former President Van Buren accepted the group's presidential nomination. Van Buren endorsed the position that slavery should be excluded from the territories acquired from Mexico, further declaring his belief that slavery was inconsistent with the "principles of the Revolution". Because Van Buren had favored the gag rule and had generally accommodated pro-slavery leaders during his presidency, many Liberty Party leaders and anti-slavery Whigs were unconvinced as to the sincerity of Van Buren's anti-slavery beliefs. Historian A. James Reichley writes that, while resentment stemming from his defeat at the 1844 Democratic National Convention may have played a role in his candidacy, Van Buren ran on the grounds that "the long-term welfare of [the Democratic Party], and the nation, required that the [Democratic Party] shed its Calhounite influence, even at the cost of losing an election or two."
With mix of Democratic, Whig, and Liberty Party attendees, the National Free Soil Convention convened in Buffalo early August. Anti-slavery leaders made up a majority of the attendees, but the convention also attracted some Democrats and Whigs who were indifferent on the issue of slavery but disliked the nominee of their respective party. Salmon Chase, Preston King, and Benjamin Franklin Butler led the drafting of a platform that not only endorsed the Wilmot Proviso but also called for the abolition of slavery in Washington, D.C. and all U.S. territories. With the backing of most Democratic delegates, about half of the Whig delegates, and a small number of Liberty Party leaders, Van Buren defeated John P. Hale to win the fledgling party's presidential nomination. For vice president, the Free Soil Party nominated Charles Francis Adams Sr., the youngest son of the recently-deceased John Quincy Adams. 
Some Free Soil leaders were initially optimistic that Van Buren could carry a handful of Northern states and force a contingent election in the House of Representatives, but Van Buren did not win a single electoral vote. However, the nomination of Van Buren alienated many Whigs; except in northern Ohio, most Whig leaders and newspapers rallied around Taylor's candidacy. Ultimately, Taylor won the election with a majority of the electoral vote and a plurality of the popular vote, improving on Clay's 1844 performance in the South and benefiting from the defection of many Democrats to Van Buren in the North. Van Buren won ten percent of the national popular vote and fifteen percent of the popular vote in the Northern states; he received a popular vote total five times greater than that of Birney's 1844 candidacy. Van Buren was the first third party candidate in U.S. history to win at least ten percent of the national popular vote. In concurr
Free Soil Party