The Democratic Party was bitterly split between War Democrats and Peace Democrats, a group further divided among competing factions.
Moderate Peace Democrats who supported the war against the Confederacy, such as Horatio Seymour, were preaching the wisdom of a negotiated peace.
After the Union victory at the Battle of Gettysburg in 1863, moderate Peace Democrats proposed a negotiated peace that would secure Union victory.
They believed this was the best course of action, because an armistice could finish the war without devastating the South.
Radical Peace Democrats known as Copperheads, such as Thomas H. Seymour, declared the war to be a failure and favored an immediate end to hostilities without securing Union victory.

George B. McClellan vied for the presidential nomination.
Additionally, friends of Horatio Seymour insisted on placing his name before the convention, which was held in Chicago, Illinois, on August 29–31, 1864.
But on the day before the organization of that body, Horatio Seymour announced positively that he would not be a candidate.

Since the Democrats were divided by issues of war and peace, they sought a strong candidate who could unify the party.
The compromise was to nominate pro-war General George B. McClellan for president and anti-war Representative George H. Pendleton for vice-president.
McClellan, a War Democrat, was nominated over the Copperhead Thomas H. Seymour.
Pendleton, a close associate of the Copperhead Clement Vallandigham, balanced the ticket, since he was known for having strongly opposed the Union war effort.
The convention adopted a peace platform – a platform McClellan personally rejected.
McClellan supported the continuation of the war and restoration of the Union, but the party platform, written by Vallandigham, opposed this position.
The Democratic Party was bitterly split between War Democrats and Peace Democrats, a group further divided among competing factions. Moderate Peace Democrats who supported the war against the Confederacy, such as Horatio Seymour, were preaching the wisdom of a negotiated peace. After the Union victory at the Battle of Gettysburg in 1863, moderate Peace Democrats proposed a negotiated peace that would secure Union victory. They believed this was the best course of action, because an armistice could finish the war without devastating the South. Radical Peace Democrats known as Copperheads, such as Thomas H. Seymour, declared the war to be a failure and favored an immediate end to hostilities without securing Union victory.
George B. McClellan vied for the presidential nomination. Additionally, friends of Horatio Seymour insisted on placing his name before the convention, which was held in Chicago, Illinois, on August 29–31, 1864. But on the day before the organization of that body, Horatio Seymour announced positively that he would not be a candidate.
Since the Democrats were divided by issues of war and peace, they sought a strong candidate who could unify the party. The compromise was to nominate pro-war General George B. McClellan for president and anti-war Representative George H. Pendleton for vice-president. McClellan, a War Democrat, was nominated over the Copperhead Thomas H. Seymour. Pendleton, a close associate of the Copperhead Clement Vallandigham, balanced the ticket, since he was known for having strongly opposed the Union war effort. The convention adopted a peace platform – a platform McClellan personally rejected. McClellan supported the continuation of the war and restoration of the Union, but the party platform, written by Vallandigham, opposed this position.
1864 United States presidential election