Brenda Wineapple’s riveting new account of the impeachment of President Andrew Johnson contains no mention of President Trump. But Wineapple has written a stunningly well-timed book on a question ripped from the headlines. Should we think of impeaching a lawless and toxic president as a vital matter of national principle? Or as an affair of pragmatic politics?

Johnson was a “vain, vulgar, and vindictive” president. A Democrat from Tennessee, he became president upon Abraham Lincoln’s assassination at the end of the Civil War in 1865. He was poorly positioned to lead a country emerging into the age of emancipation. Johnson had owned eight or nine slaves before the war; he may have fathered several of them. He openly espoused white supremacy. Unlike most of his fellow statesmen in the South, however, he opposed secession. He called it treason and charged the South’s plantation-owning elite with abandoning the Constitution. Lincoln rewarded him with the post of military governor of Tennessee in 1862. Two years later, the Republican Party chose Johnson as Lincoln’s running mate in hopes of attracting Democratic votes in the crucial presidential race of 1864. Lincoln’s assassination made him an accidental president.

Republicans held out hope that as president Johnson would embrace the party’s policies. He had come around to support emancipation, though as Wineapple observes, he did so on the ground that ending slavery would “liberate the white man,” not because it would free African Americans. (Blacks, Johnson insisted, had benefited from captivity.) As 1865 proceeded, Johnson’s real sympathies became clear: He pardoned former rebels. He restored confiscated lands to rebel owners. Johnson recognized new Southern state governments led by former slaveholding whites. He defended draconian state laws limiting the freedom of former slaves.

In 1866, Johnson moved aggressively to block the Republican Party agenda. He vetoed an extension of the Freedmen’s Bureau, which Congress had established to administer abandoned lands and provide aid to African Americans in the South. He vetoed the Civil Rights Bill, too, which promised rights of contract and basic legal protections. Moderate Republicans had championed the bill as a conservative alternative to more radical measures like land redistribution and voting rights for black men. But Johnson’s zero-sum racial outlook led him to insist that simple equality guarantees actually “operated ‘in favor of the colored and against the white race.’ ”