This education gave him a moral vision that emerged from life, not from reading.

He saw America as a land where ambitious poor boys and girls like himself could transform themselves through hard, morally improving work. He believed in a government that built canals and railroads and banks to stoke the fires of industry. He believed slavery was wrong in part because people should be free to control their own labor. He believed in a providence that was active but unknowable.

This Whiggish vision was his north star. He could bob and weave as politics demanded, but his incremental means always pointed to the same transformational end. Any presidential candidate needs that sort of consistent animating vision — an image of an Ideal America baked so deeply into his or her bones as to be unconscious, useful as a compass when the distractions of Washington life come in a flurry.

Lincoln’s temperament surpasses all explanation. His early experience of depression and suffering gave him a radical self-honesty. He had the double-minded personality that we need in all our leaders. He was involved in a bloody civil war, but he was an exceptionally poor hater. He was deeply engaged, but also able to step back; a passionate advocate, but also able to see his enemy’s point of view; aware of his own power, but aware of when he was helpless in the hands of fate; extremely self-confident but extremely humble. Candidates who don’t have a contradictory temperament have no way to check themselves and are thus dangerous.

Lincoln’s skills as a political tactician seem like the least of his gifts, but are among his greatest. It’s easy to be a true believer, or to govern or campaign with your pedal to the metal all the time. It’s much harder to know when to tap on the brake and when to step on the gas.

We study Lincoln’s tactical phase shifts in the Grand Strategy class I help with at Yale. There’s never enough time to cover them all.