Answer:
President Lincoln's advisors who were against the Emancipation Proclamation were concerned that it could negatively affect the Union's military efforts during the Civil War. Specifically, they worried that it could push border states that were still loyal to the Union, such as Kentucky and Maryland, into secession and into joining the Confederacy.
Additionally, some feared that the proclamation could undermine public support for the war effort and hurt the Union's chances of victory. They also worried about potential backlash from Northerners who were opposed to abolition and could potentially vote against Lincoln in the upcoming 1864 presidential election.
Despite these concerns, President Lincoln ultimately believed that issuing the Emancipation Proclamation was a necessary step in ending slavery and winning the war. He saw slavery as a moral issue and thought that it was incompatible with the principles of the Declaration of Independence and the Constitution.
In addition to the moral imperative, Lincoln saw the Emancipation Proclamation as a way to undermine the Confederacy's economic and military power. By freeing slaves in the Confederacy, he hoped to weaken the South's labour force and deprive it of a crucial source of support.
Overall, Lincoln believed that issuing the Emancipation Proclamation was essential for the Union's ultimate victory and the preservation of the nation's founding principles.