There’s precedent for making transgressive presidential speech a “high crime or misdemeanor.” The 10th article of impeachment against Andrew Johnson in 1868 was about his language and conduct over the course of his term. Two years earlier, Johnson had taken a tour of Northern cities to campaign against Radical Republicans in Congress and build support for his lenient policies toward the defeated South.

At first, it was a success, with large crowds cheering the president during events in Baltimore, New York and Philadelphia. But his fortunes turned in Cleveland, where the stubborn and taciturn Johnson unraveled in the face of hecklers. “The president was frequently interrupted by cheers, by hisses and by cries, apparently from those opposed to him in the crowd,” William Hudson, a reporter for The Cleveland Leader, wrote. When a heckler yelled, “Hang Jeff Davis!” — referring to the former leader of the Confederacy, then held at Fort Monroe in Virginia — Johnson replied, “Why don’t you hang him?” When another shouted, “Thad Stevens” — the chief Radical Republican in the House of Representatives — a now angry Johnson responded with “Why don’t you hang Thad Stevens and Wendell Phillips?” Phillips had been a leading abolitionist.

Johnson continued to speak, struggling to gain the upper hand with the crowd. By the end, however, the president was unhinged. “Come out where I can see you,” he said to one heckler. “If you ever shoot a man, you will do it in the dark and pull the trigger when no one else is by to see.” After witnessing this disastrous performance, an aide urged the president to consider the dignity of the office. Johnson was dismissive. “I don’t care about my dignity,” he reportedly said.

The tour didn’t improve. In St. Louis, as in Cleveland, hecklers yelled “New Orleans” in reference to a massacre that summer in which white Democrats, most of them ex-Confederates, attacked a large gathering of black Republican marchers, killing nearly 50 people. In response, Johnson said the “riot at New Orleans was substantially planned.” But he blamed Radical Republicans who, he said, encouraged the city’s “black population to arm themselves and prepare for the shedding of blood.” At this point, someone in the crowd called him a “traitor,” which — as Garry Boulard recounts in “The Swing Around the Circle: Andrew Johnson and the Train Ride That Destroyed a Presidency” — Johnson angrily denounced with one of the strangest tirades of the tour: “I have been traduced! I have been slandered. I have been maligned. I have been called Judas — Judas Iscariot and all of that.”

By the time it was over, Johnson had been humiliated and his reputation was in tatters. In The Atlantic Monthly, the essayist Edwin Percy Whipple summarized elite opinion of Johnson’s tour :

Never before did the first office in the gift of the people appear so poor an object of human ambition as when Andrew Johnson made it an eminence on which to exhibit inability to behave and incapacity to reason. His low cunning conspired with his devouring egoism to make him throw off all the restraints of official decorum, in the expectation that he would find duplicates of himself in the crowds he addressed and that mob diffused would heartily sympathize with Mob impersonated. Never was a blustering demagogue led by a distempered sense of self-importance into a more fatal error.

All of this would resurface in 1868, when the House adopted its 11 articles of impeachment against the president. Among them was a reference to his summer swing through the North — to the idea that Johnson had sullied the office of the presidency with dangerous, demagogic rhetoric. In its 10th article of impeachment, the House of Representatives accused Johnson of being “unmindful of the high duties of his office and the dignity and proprieties thereof.” His behavior, they argued, was an “attempt to bring into disgrace, ridicule, hatred, contempt and reproach the Congress of the United States” and to “impair and destroy the regard and respect of all the good people of the United States for the Congress and the legislative power thereof.”