Basically, Lincoln did in 1864. Lincoln was a Republican and chose fellow Republican Hannibal Hamlin as his running mater in 1860. When Lincoln sought reelection in 1864, he pushed Hamlin off of the ticket and chose Andrew Johnson as his Vice President. Johnson was a Democrat — the only Southern Senator to oppose his state’s secession and remain in the Senate. While Lincoln and Johnson technically ran in 1864 under the coalition “National Union” party, Lincoln was a Republican at heart and Johnson was a Democrat. In fact, Lincoln dumped Hamlin from the ticket in order to balance it. He saw that the war was coming to a close and was beginning to think of Reconstruction, so he balanced it with the pro-Union Southern Democrat Johnson who Lincoln also wanted to reward for his loyalty to the Union first rather than his home state.