The (post-dated) issue of Harper's Weekly carrying this cartoon was published on April 25, two days after the Democratic National Convention convened in Charleston, South Carolina, but before its outcome was known.  The Southern Democratic delegates had arrived at the convention determined to have their party endorse in its platform a federal slave code for the territories.  They believed that if Congress did not enact a federal slave code, then most Western territories would enter the Union as free states, thus allowing the eventual passage of a Constitutional amendment abolishing slavery everywhere.  Northern Democrats, led by Senator Stephen Douglas of Illinois, opposed endorsing a federal slave code.  They wanted the territories to remain free from federal interference, with territorial voters able to judge the slavery issue for themselves on the basis of popular sovereignty.

Douglas was the leading candidate for the Democratic presidential nomination, but he faced competition primarily from Senator Robert Hunter, former treasury secretary James Guthrie of Kentucky, and Senator Andrew Johnson of Tennessee (not pictured).  Douglas had been weakened politically by his bitter and public struggle with President James Buchanan over the issue of slavery in the Kansas Territory.  Douglas’s stance on slavery in the territories had undermined much of his support in the South, and he faced well-organized opposition to his nomination.  

After rancorous debate, the convention narrowly adopted Douglas's resolution that endorsed Congressional non-interference, rather than a federal slave code.  That provoked most of the Southern delegates to leave the convention.  The remaining delegates attempted to nominate a presidential candidate.  Although Douglas held a clear majority over Hunter and Guthrie, he was not able to reach the two-thirds requirement.  On May 3, after 57 ballots, delegates decided to adjourn and reconvene in Baltimore, Maryland, on June 18, at which time they nominated Douglas for president.  Meanwhile, the splinter group of Southern Democrats nominated Vice President John Breckinridge for president.

Consequently, in the general election in November 1860, the Democratic Party was divided into regional factions that had split over the issue of slavery in the territories.  This allowed the nominee of the Northern-based Republican Party, Abraham Lincoln, to win a majority in the Electoral College (although only a plurality in the popular vote) and become president-elect.