This was the only time in U.S. history in which a political party denied renomination to the incumbent President and won . Incumbent Democratic President Franklin Pierce was widely unpopular due to the ongoing civil war in Kansas Territory , and Buchanan defeated Pierce at the 1856 Democratic National Convention . Buchanan , a former Secretary of State , had avoided the divisive debates over the Kansas – Nebraska Act by virtue of his service as the Ambassador to the United Kingdom . Slavery , though not its abolition , was the main issue . Opposition to the extension of slavery into the territories drove the rise of the nascent Republican Party . The Republicans and the nativist Know Nothings ( known formally as the American Party ) competed to replace the moribund Whig Party as the primary opposition to the Democrats . 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 . His political allies controlled the American Party and he welcomed the nomination , but Fillmore had not sought it and was in Europe during the nominating convention . Severe domestic political turmoil at the time of the election was clearly represented by the nominations of Buchanan and Fillmore , who appealed in part because of their recent time abroad and the ability to avoid social issues . The Democrats endorsed popular sovereignty as the method to determine slavery 's legality for newly admitted states . Frémont decried the expansion of slavery , while Buchanan warned that the Republicans were extremists whose victory would lead to civil war . 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
1856 Democratic National Convention
1856 Democratic National Convention
1856 United States presidential election