From Peter Wehner's The Role of Sympathy and Trust in American Politics:
This is admittedly a complicated area, as some of our greatest presidents pursued policies that caused deep divisions. President Lincoln is a particularly fascinating case study. He presided over a Civil War that led to the death of around 620,000 people in a nation of roughly 30 million. And yet, as the Lincoln biographer Ronald C. White, Jr. has said, his second inaugural address called the whole nation to account and offered a moral framework for peace and reconciliation. When passions were at their highest and the North was at its strongest, Lincoln held out a path for reunification instead of revenge.