In 1849, when Abraham Lincoln returned to Springfield, Illinois, after two seemingly uninspiring years in the U.S. House of Representatives, his political career appeared all but finished. He attempted to revive his law practice but was dismissed from the biggest case of his career six years later. As Lincoln’s spirits dimmed, his Democratic rival, Stephen Douglas, an advocate for slavery, became a senator and rising star. Distraught, Lincoln’s sense of failure was so great that friends worried about his sanity. Yet within a decade, Lincoln would reenter politics, become a leader of the Republican Party, win the 1860 presidential election, and keep America together during its most perilous period. Lincoln learned valuable lessons on leadership, mastering party politics, campaigning, conventions, understanding and using executive power, managing a cabinet, speechwriting and oratory, and—what would become his most enduring legacy—developing policies and rhetoric to match a constitutional vision that spoke to the monumental challenges of his time.