Abraham Lincoln "repeatedly asserted that his aim was to prevent the spread of slavery, not eliminate it in the South." When asked if he was going to outlaw slavery in the South he would reply, "I believe I have no lawful right to do so."
Then, two years into the war (of "Northern Aggression" LOL) he issued his "Emancipation Proclamation".
The North claimed Lincoln had "lied" and "misled the country into war" and that a "bloody and unnecessary war was being fought to bring the blessings of democracy to a people who had little experience with it."
Lincoln was also criticized for suspending habeas corpus -and not asking Congressional permission to do so until long afterwards.
Throughout the conflict embittered Democrats claimed the war was an utter failure and demanded the administration bring the soldiers home.
The active duty commander, Gen. George McClellan (backed by the "Peace Democrats"), chastised Lincoln for predicting a shorter war with far less casualties...and for not sending enough troops.
(From: Team of Rivals: The Political Genius of Abraham Lincoln -Doris Kearns Goodwin)
(Book Recommendation H/T: Real Clear Politics)