Incumbent President Abraham Lincoln of the National Union Party easily defeated the Democratic nominee, former General George B. McClellan, by a wide margin of 212–21 in the electoral college, with 55% of the popular vote.

Rather than re-nominate Vice President Hannibal Hamlin, the convention selected Andrew Johnson of Tennessee, a War Democrat, as Lincoln's running mate.

Despite his early fears of defeat, Lincoln won strong majorities in the popular and electoral vote, partly as a result of the recent Union victory at the Battle of Atlanta.

Lincoln was assassinated less than two months into his second term, and he was succeeded by his vice president, Andrew Johnson, who favored quick restoration of the seceded states to the Union without protection for the former slaves.

According to the Miller Center for the study of the presidency, the election was noteworthy for occurring at all, an unprecedented democratic exercise in the midst of a civil war.

War Democrats joined with Republicans as the National Union Party, with Lincoln at the head of the ticket.

National Union candidates: As the Civil War progressed, political opinions within the Republican Party began to diverge.

Senators Charles Sumner and Henry Wilson from Massachusetts wanted the Republican Party to advocate constitutional amendments to prohibit slavery and guarantee racial equality before the law.

The New York World also published false information (further purported by Samuel S. Cox) to limit Lincoln's popularity.

[8] With the outcome of the Civil War still in doubt, some political leaders, including Salmon P. Chase, Benjamin Wade, and Horace Greeley, opposed Lincoln's re-nomination on the grounds that he could not win.

[9] The party platform included these goals: "pursuit of the war, until the Confederacy surrendered unconditionally; a constitutional amendment for the abolition of slavery; aid to disabled Union veterans; continued European neutrality; enforcement of the Monroe Doctrine; encouragement of immigration; and construction of a transcontinental railroad."

In his congressional service, he sought passage of the Homestead Bill which was enacted soon after he left his Senate seat in 1862.

In 1864, Johnson was a logical choice as running mate for Lincoln, who wished to send a message of national unity in his re-election campaign, especially to ensure the electoral votes of the border states.

[11] 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.

Additionally, friends of Horatio Seymour insisted on placing his name before the convention, which was held in Chicago, Illinois, on August 29–31, 1864.

Since the Democrats were divided by issues of war and peace, they sought a strong candidate who could unify the party.

Pendleton, a close associate of the Copperhead Clement Vallandigham, balanced the ticket, since he was known for having strongly opposed the Union war effort.

[15] McClellan supported the continuation of the war and restoration of the Union, but the party platform, written by Vallandigham, opposed this position.

In his statement, Frémont declared that winning the Civil War was too important to divide the Republican vote.

Lastly, the storming of Mobile bay on August and the fall of Atlanta on September 2, public confidence in the war effort was restored to the belief that victory is closer than thought.

[19] In the end, the Union Party mobilized the full strength of both the Republicans and the War Democrats under the slogan "Don't change horses in the middle of a stream".

It was energized as Lincoln made emancipation the central issue, and state Republican parties stressed the perfidy of the Copperheads.

They chose presidential electors, but their votes were rejected by Congress due to having recently seceded from the Union.

[23][24] The following states allowed soldiers to cast ballots: California, Kansas, Kentucky, Maine, Michigan, Rhode Island, and Wisconsin.

Had they not been rejected, Lincoln would have received 229 electoral votes out of a total of 251 (250 cast), well in excess of the 126 required to win.