Lincoln ran for reelection in 1864, while uniting the main Republican factions, along with War Democrats Edwin M. Stanton and Andrew Johnson. Lincoln used conversation and his patronage powers—greatly expanded from peacetime—to build support and fend off the Radicals' efforts to replace him. At its convention, the Republicans selected Johnson as his running mate. To broaden his coalition to include War Democrats as well as Republicans, Lincoln ran under the label of the new Union Party.

The Democratic platform followed the "Peace wing" of the party and called the war a "failure"; but their candidate, McClellan, supported the war and repudiated the platform. Meanwhile, Lincoln emboldened Grant with more troops and Republican party support. Sherman's capture of Atlanta in September and David Farragut's capture of Mobile ended defeatism. The Democratic Party was deeply split, with some leaders and most soldiers openly for Lincoln. The National Union Party was united by Lincoln's support for emancipation. State Republican parties stressed the perfidy of the Copperheads. On November 8, Lincoln carried all but three states, including 78 percent of Union soldiers.