One of the reasons to coalesce under the Union Party label was to blunt the threat that Fremont-- who had strong abolitionist support-- posed by running in 1864. A three way race threatened to siphon off votes from Lincoln allowing a McClellan win. Fremont did not officially withdraw until late September. With Fremont gone from the race it was seen as too late to revert back to a strictly Republican label, and commitments had already been made.
All of these early possible candidates disavowed interest in advance of the convention. However, the strident antislavery forces coalesced around the candidacy of
John C. Frémont , a bitter foe of Lincoln. The president had twice dismissed Frémont from military commands and had reversed his order to free the slaves in Missouri in 1861. These antislavery forces held an early convention in Cleveland and nominated Frémont.
The regular Republican Party met in Baltimore and used the name National Unity Party in the hope of attracting War Democrats. Lincoln was selected on the first ballot and offered no preference for a running mate. The convention chose
Andrew Johnson of Tennessee, a seemingly attractive candidate thanks to his Southerner and War Democrat background. The platform promised to prosecute the war effort until the
Confederacy's "unconditional surrender."
During the campaign, Frémont relinquished his bid, fearing that he would split the Republican vote and enable the Democrats to win. The turning point came in early September with Sherman's
capture of Atlanta, a victory that lifted spirits throughout the North and revitalized the Lincoln campaign. The Republicans warned the voters, "Don't change horses in the middle of the stream."
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