**An instant New York Times bestsellerA nuanced exploration of Abraham Lincoln’s political acumen, illuminating a great politician’s strategy in a country divided—and lessons for our own disorderly present**In 1855, with the United States at odds over slavery, the lawyer Abraham Lincoln wrote a note to his best friend, the son of a Kentucky slaveowner. Lincoln rebuked his friend for failing to oppose slavery. But he added: “If for this you and I must differ, differ...