Presidential elections were held in the United States on November 4, 1856. Democratic nominee James Buchanan defeated Republican nominee John C. Frémont and Know Nothing/Whig nominee Millard Fillmore. The main issue was the expansion of slavery as facilitated by the Kansas–Nebraska Act of 1854. Buchanan defeated President Franklin Pierce at the 1856 Democratic National Convention for the nomination. Pierce had become widely unpopular in the North because of his support for the pro-slavery faction in the ongoing civil war in territorial Kansas, and Buchanan, a former Secretary of State, had avoided the divisive debates over the Kansas–Nebraska Act by being in Europe as the Ambassador to the United Kingdom.

Slavery was the main issue, and with it the question of the survival of the United States as it then existed. The Democrats were the pro-slavery party. While the new Republican party was hostile to slavery, they limited their efforts to the politically more manageable question of the extension of slavery into federal territories (and its removal from the District of Columbia). The nativist Know Nothings (known formally as the American Party) competed with the Republicans to replace the moribund Whig Party as the primary opposition to the Democrats. They emphasized opposition to Catholic immigrants.

The 1856 Republican National Convention nominated a ticket led by Frémont, an explorer and military officer who had served in the Mexican–American War. The Know Nothings, who ignored slavery and instead emphasized anti-immigration and anti-Catholic policies, nominated a ticket led by former Whig President Millard Fillmore. Domestic political turmoil was a major factor in the nominations of both Buchanan and Fillmore, who appealed in part because of their recent time abroad, when they did not have to take a position on the divisive questions related to slavery.

The Democrats supported expansionist slave-holding policies generally of varying intensities. Southern Democrats were all in favor of the expansion of slavery. Some wanted to obtain Cuba as slave territory, as espoused by the Ostend Manifesto. Northern Democrats called for "popular sovereignty", which in theory would allow the residents in a territory to decide for themselves the legal status of slavery. In practice, in Kansas Territory, it produced a state-level civil war. Frémont opposed the expansion of slavery. Buchanan called that position "extremist", warning that a Republican victory would lead to disunion, a then constant issue of political debate which had already been long discussed and advocated. The Know Nothings attempted to present themselves as the one party capable of bridging the sectional divides. All three major parties found support in the North, but the Republicans had virtually no backing in the South.

Buchanan won a plurality of the popular vote and a majority of the electoral vote, taking all but one slave state and five free states. Frémont won a majority of electoral votes from free states and finished second in the nationwide popular vote, while Fillmore took 21.5% of the popular vote but only carried Maryland. The Know Nothings soon collapsed as a national party, as most of its anti-slavery members joined the Republican Party after the 1857 Dred Scott v. Sandford Supreme Court ruling. This election marked the end of the Second Party System and also proved to be the last Democratic presidential victory until Grover Cleveland in 1884, as Republicans emerged as the dominant party during and after the Civil War.

Nominations The 1856 presidential election was primarily waged among three political parties, though other parties had been active in the spring of the year. The conventions of these parties are considered below in order of the party's popular vote.

Democratic Party nomination

1856 Democratic Party ticket for Presidentfor Vice President U.S. Minister to Great Britain(1853–1856) U.S. Representativefor Kentucky's 8th(1851–1855)

Democratic candidates: James Buchanan, Minister to Great Britain and former Secretary of State Franklin Pierce, President of the United States Stephen Douglas, U.S. Senator from Illinois Lewis Cass, U.S. Senator and 1848 presidential nominee from Michigan

The Democratic Party was wounded from its devastating losses in the 1854–1855 midterm elections. Senator Stephen A. Douglas of Illinois, who had sponsored the Kansas-Nebraska Act, entered the race in opposition to President Franklin Pierce. The Pennsylvania delegation continued to sponsor its favorite son Buchanan.

The Seventh Democratic National Convention was held in Smith and Nixon's Hall in Cincinnati, Ohio, on June 2 to 6, 1856. The delegates were deeply divided over slavery. On the first ballot, Buchanan placed first with 135.5 votes to 122.5 for Pierce, 33 for Douglas, and 5 for Senator Lewis Cass, who had been the presidential nominee in 1848. With each succeeding ballot, Buchanan gradually extended his lead, while Douglas began making significant gains at Pierce's expense. By the end of the first day, with 14 ballots having been completed, it was clear that Pierce would not be nominated for a second term, and he withdrew his name from contention. On the 15th ballot, most of Pierce's delegates shifted to Douglas in an attempt to stop Buchanan, but Douglas withdrew when it became clear Buchanan had the support of the majority of those at the convention, also fearing that his continued participation might lead to divisions within the party that could endanger its chances in the general election. For the first time in American history someone who had been elected president was denied re-nomination after seeking it.

A host of candidates were nominated for the vice presidency, but a number of them attempted to withdraw themselves from consideration, among them the eventual nominee, John C. Breckinridge of Kentucky. Breckinridge, besides having been selected as an elector, was also supporting former Speaker of the House Linn Boyd for the vice presidential nomination. However, following a draft effort led by the delegation from Vermont, Breckinridge was nominated on the second ballot.

Republican Party nomination

1856 Republican Party ticket for Presidentfor Vice President U.S. Senator from California(1850–1851) U.S. Senator from New Jersey(1842–1851)

Republican candidates: John C. Frémont, former United States Senator from California John McLean, Associate Justice of the United States Supreme Court

The Republican Party was formed in early 1854 to oppose the Kansas-Nebraska Act. During the midterm elections of 1854–1855, the Republican Party was one of the patchwork of anti-administration parties contesting the election, but they were able to win thirteen seats in the House of Representatives for the 34th Congress. However, the party collaborated with other disaffected groups and gradually absorbed them. In the elections of 1855, the Republican Party won three governorships.

The first Republican National Convention was held in the Musical Fund Hall in Philadelphia, Pennsylvania, on June 17 to 19, 1856. The convention approved an anti-slavery platform that called for congressional sovereignty in the territories, an end to polygamy in Mormon settlements, and federal assistance for a transcontinental railroad—a political outcome of the Pacific Railroad Surveys. John C. Frémont, John McLean, William Seward, Salmon Chase, and Charles Sumner all were considered by those at the convention, but the latter three requested that their names be withdrawn. Seward and Chase did not feel that the party was yet sufficiently organized to have a realistic chance of taking the White House and were content to wait until the next election. Sumner was in no fit condition to run after being violently assaulted on the Senate floor a month before the convention. McLean's name was initially withdrawn by his manager Rufus Spalding, but the withdrawal was rescinded at the strong behest of the Pennsylvania delegation led by Thaddeus Stevens. Kentucky was the only southern state to have a delegation at the convention. Frémont was nominated for president overwhelmingly on the formal ballot, and William L. Dayton was nominated for vice president over Abraham Lincoln.

American (Know-Nothing) Party nomination

1856 American Party ticket for Presidentfor Vice President 13thPresident of the United States(1850–1853) 2ndU.S. Envoy to Prussia(1846–1849)

American Party candidates:

Millard Fillmore, former President of the United States from New York George Law, steamboat entrepreneur from New York

The American Party, formerly the Native American Party, was the vehicle of the Know Nothing movement. The American Party absorbed most of the former Whig Party that had not gone to either the Republicans or Democrats in 1854, and by 1855 it had established itself as the chief opposition party to the Democrats. In the 82 races for the House of Representatives in 1854, the American Party ran 76 candidates, 35 of whom won. None of the six independents or Whigs who ran in these races were elected.

The party gained control over the state governments of California, Connecticut, Massachusetts, New Hampshire, and Rhode Island in the 1854 and 1855 elections. The party also controlled the Tennessee legislature and received at least 45% of the vote in multiple Southern states, far better than the Whig Party following 1848. The party then succeeded in electing Nathaniel P. Banks as Speaker of the House in the 34th Congress.

However, the party started to break apart at sectional lines over slavery. Henry Wilson led Northern delegates out of the party's 1855 national council in Philadelphia in protest of it adopting a plank endorsing the Kansas-Nebraska Act. 70 Northern delegates left the 1856 convention to create the North American Party after a resolution calling for the Kansas-Nebraska Act to be repealed was defeated.

The American National Convention was held in National Hall in Philadelphia, Pennsylvania, on February 22 to 25, 1856. Following the decision by party leaders in 1855 not to press the slavery issue, the convention had to decide how to deal with the Ohio chapter of the party, which was vocally anti-slavery. The convention closed the Ohio chapter and re-opened it under more moderate leadership. Delegates from New England, Pennsylvania, Ohio, Illinois, Iowa, and other Northern states bolted when a resolution that would have required all prospective nominees to be in favor of prohibiting slavery north of the 36'30' parallel was voted down. This removed a greater part of the American Party's support in the North outside of New York, where the conservative faction of the Whig Party remained faithful.