Why was Lincoln reelected?

He was winning the war. With victory in Atlanta, and the siege of Petersberg, Virginia (near Richmond), the Union was going to win the war, and President Abraham Lincoln was getting rid of slavery. General George McClellan, the Democratic nominee for President was a terrible, wimpy general, and he looked like the sort of leader who would give everything away in order to end the war, and might even support slavery. Almost nobody voted for McClellan, instead of President Lincoln.