In 1860, the United States was divided over the issue of slavery. Four major political parties nominated candidates in the 1860 presidential election. Incumbent president James Buchanan, a Democrat, did not seek re-election. The anti-slavery Republican Party nominated Abraham Lincoln, a former one-term Whig Representative from Illinois, for president. Its platform promised not to interfere with slavery in the South, but opposed extension of slavery into the territories. A group of former Whigs and Know Nothings formed the Constitutional Union Party, which sought to avoid disunion by resolving divisions over slavery with some new compromise. The 1860 Constitutional Union Convention put forward former Tennessee Senator John Bell for president. After the 1860 Democratic National Convention adjourned without agreeing on a nominee, a second convention nominated Illinois Senator Stephen A. Douglas as the Democratic presidential candidate. Douglas's support for the concept of popular sovereignty, which called for each territory's settlers to decide locally on the status of slavery, alienated many radical pro-slavery Southern Democrats. With President Buchanan's support, Southern Democrats held their own convention, nominating Vice President John C. Breckinridge of Kentucky for president.