At the outset of the Civil War, Abraham Lincoln appeared to be a "conservative" on the subject of slavery. Unlike the radical elements of his Republican party, Lincoln was not an abolitionist. During the Lincoln/Douglas debates of the 1850s, and during the Presidential campaign of 1860, his stance was "status quo." He opposed slavery as a concept -- condemning it as a social evil, yet he was willing to allow it to continue to exist in the states where it was legal because it was so deeply ingrained in Southern society as well as sustained by the Constitution. The one thing he was not willing to compromise on was slavery must not expand into any new territory the United States had acquired, or into any new States that might be admitted to the Union.
Besides the Constitutional argument, Lincoln was walking a tight rope as he took office in 1860. Several of the slave states had chosen not to join the Confederacy -- the "border states" -- and Lincoln needed to do what he could to keep them in the fold. His first inaugural address dealt with the concept of compromise -- a willingness to keep any seceding State in the Union, even to protect such a State's slave holders with added legal measures, if that would preserve the Union. After the war started, when Union generals and even a member of his own cabinet issued bold, anti-slavery statements, Lincoln censured them, declaring that only he had the power to change the administration's stance on slavery.
But as the War ground on into its second year, in the summer of 1862, the subject of slavery became more and more a part of the debate on why the war was being waged. Even the neo-Confederates of today will argue the war wasn't fought over slavery, but for "state's rights." Many of the "conservative" elements of the 1862 political scene tried to frame the issues in a similar way. But even when Congress was debating some other measure -- a banking bill, or war finances, or tariffs -- the argument would invariably stray back into how the nation would deal with the question of slavery.
And the attitudes in the North were changing. Slavery had almost been a taboo subject before the war, for fear of offending powerful southern politicians. But now, seeing that slavery was the genesis of the destruction of the Union, much of the opinion in the North turned against the slaveholders, holding them responsible for the war. And President Lincoln's own personal views seemed to be evolving as well.
Lincoln's "official" stance on the slavery question remained "status quo," that is, without a Constitutional Amendment, it would still be legal in the southern states where it was practiced, but he adamantly opposed allowing it to expand elsewhere. But in some of his speeches, and in his private correspondence, he began formulating a concept for emancipation.
Then, in the spring of 1862, Lincoln proposed a joint administrative/congressional resolution providing federal aid to any state willing to commit to the concept of gradual emancipation. This "concept" could take on a variety of forms -- the resolution suggested slaves being set free upon reaching a certain age, or the state setting a date certain when slavery would be abolished. The federal dollars would be used to recompense the slave owners for the value of their "property." Privately, Lincoln shared that if the border states were to commit to end slavery, there would be no chance they would join the Confederacy in the future, and he hoped this would help the Confederate cause to "lose heart."
The joint resolution met received little support. Many argued that it would be unfair to "punish" the slaveholders in the loyal states by forcing them to radically alter their society, while the rebel states retained their slaves. There was also a sense that the Federal treasury couldn't handle the cost.
At the same time, however, Congress took it upon itself to pass a bill calling for a similar plan for compensated emancipation for the District of Columbia. Lincoln did not hesitate to sign the bill, declaring that he always believed that congress could abolish slavery in the territory under its own jurisdiction.
Then, Congressional "radicals" began to attempt to reach into the Confederacy to fight slavery. Earlier, Congress had passed a "confiscation" act, aimed at seizing the property of those openly rebelling against the United States in military conflict. This first bill had only called for the capture of slaves who were being used to participate in military activities (digging earthworks at the front, acting as support for the troops, etc.), while leaving the slaves tending farms alone. The new bill went a lot further, calling for the confiscation of all property of any person supporting the rebellion, even if not involved in military action. Presumably, this meant the slaves of Confederate officers who staid home to tend the plantation in thier master's absence.
This new bill, known as the "Second Confiscation Act," was highly controversial, as it moved into the realm of a matter presumably guaranteed by the Constitution. The editors of the nation's newspapers were surprised when Lincoln signed the bill into law.
The debates over slavery continued to mount, becoming more and more bitter. Every debate on the House or Senate floor became an argument over the viability of slavery. Even in Lincoln's cabinet, the secretaries of the various departments chose sides, and their meetings were filled with side bars about how far to go to allow for or ban slavery, to the point where official business was often shelved. Lincoln appeared to generally not take part in these debates -- he listened, taking it all in. When he did comment, Lincoln insisted that as President, he couldn't take sides. He agreed with the abolitionists that slavery was a "moral, a social, and a political wrong," but felt compelled by the Constitution to allow for it in the states where it already existed.
But depressing turns the war was taking gave Lincoln pause. The Union Army had suffered defeat after crushing defeat, particularly in the fields of Northern Virginia, just a few miles from Washington, D.C. Lincoln began to look for more creative, even more drastic measures to save the Union and turn the tide of the war. He began to consider attacking slavery as the means to reach his goal.
It was clear that at least on the battlefield, the slave owning Confederates had an unfair advantage. Slaves were used to support the army. They dug trenches, built fortifications, served as cooks, stable hands, laborers, and hospital workers. Even more galling, most of the slaves staid home to tend the fields while their masters went to war -- the average southern gentleman could rest assured his family back home was being provided for, while the northern soldier had to leave his family to fend for themselves.
But even more important, if the south was deprived of its slave labor, and that labor force was transformed into recruits to join the Union army, the North would have a new advantage. Lincoln began to realize he had a new angle -- not only was eliminating slavery something that was part of a concept of higher morality, it had become a military necessity. As President, he could use his executive power as commander in chief to further the causes of the war. He began to see this as as emergency matter, that would trump the vague constitutional guarantee of a right to own slaves. The concept of compensated emancipation had been rejected in the border states in part because they argued that the government should be dealing with slavery where the rebellion was happening. Lincoln's views were evolving, and he began to consider that very move.