Johnson was, possibly, the worst man to lead the country at such a tense moment. Racist, crude, and grumpy, Johnson nursed an incredible persecution complex. At best, he was a formerly illiterate tailor who had worked his way up from poverty to the most powerful position in the nation, like his fellow Tennessean and personal hero, Andrew Jackson. At worst, he was paranoid, resentful, narcissistic. Washington politicos described a man who “always hated somebody,” “always defeats himself,” and was “always worse than you expect.”

There were, still, millions who sided with Johnson. White Democrats, especially in the lower north and the south, felt overwhelmed by Republicans. To them, Republicans were social-justice warriors intent on revolutionizing race relations and centralizing Federal power; most Democrats just wanted to return to the old union and old Constitution. Such Democrats launched the most bitterly racist campaigns in American history, rallying behind Andrew Johnson as a symbol of their struggle against change.

Johnson put his presidency on a collision course with Congress. He referred, constantly, to his unfair treatment and to his many enemies, at whom he spat bold, baseless claims. After white police officers slaughtered dozens of black activists in New Orleans, Johnson ridiculously blamed “the radical Congress” for the massacre. On a disastrous speaking tour across the Midwest—in which he drank heavily and compared himself to Jesus—Johnson called for the lynching of his most hated congressional rival, Thaddeus Stevens. Even relatively neutral observers like Senator John Sherman eventually concluded that he was beyond help, sighing: “The truth is, he is a slave to his passions and resentments.”

Johnson’s enemies were nearly as intent on conflict. They set a trap for the president, making it illegal for him to fire certain officials. Of course, Johnson promptly fired them. His nemesis, Stevens, was heard hollering in Congress: “Didn’t I tell you so? If you don’t kill the beast, it will kill you.” Congress moved in, voting for impeachment in March 1868.

But impeachment means more than merely a trial in Washington. As news spread across the nation, many citizens assumed that politics was once again bleeding over into violence. Some braced for a second Civil War, this time fought not just by north and south, but also between Republicans and Democrats in places like New Jersey and Ohio. One man in Illinois was reminded of “Fort Sumpter times. Everybody is for fight,” while a Massachusetts woman, tired of warfare, merely shrugged: “Another revolution is upon us (Heaven help us that it be a peaceful one).”

An angry president, resentful of the political establishment; a devoted minority, supporting their leader as a symbol of the country they feared they were losing; a trial which blurred the lines between legal and political charges—it was all enough, 150 years ago, to threaten renewed war. Americans live in far more peaceful times today, but it’s not difficult to imagine how impeachment could rile an already agitated nation.