The Democratic party, divided and defeated in the election of 1860, lost its Southern members in 1861 by the secession and remained a minority party during the remainder of the war.

It retained its organization, however, and in 1864 polled a large vote.

Discredited by its policy of opposition to Lincoln's administration, its ablest leaders joined the Republicans in support of the war.

Until 1869, the party was poorly represented in Congress although, as soon as hostilities ended, the War Democrats showed a tendency to return to the old party.

As to reconstruction, the party stood on the Crittenden-Johnson resolutions of 1861, though most Democrats were now willing to have slavery abolished.
The Republican party--frankly sectional and going into power on the single issue of opposition to the extension of slavery--was forced by the secession movement to take up the task of preserving the Union by war.