Last week, in defense of her father, Ivanka Trump tweeted out a quotation she wrongly attributed to Alexis de Tocqueville: “A decline of public morals in the United States will probably be marked by the abuse of the power of impeachment as a means of crushing political adversaries or ejecting them from office.”

The misquotation came from an opinion essay in The Wall Street Journal that has since been corrected. What is fascinating about this incident though, is that the quotation actually comes from an 1889 book, “American Constitutional Law,” that defends Andrew Johnson against his impeachment in 1868. By the time the book was written, emancipation and the attempt to guarantee black rights lay in shambles, and conservatives rallied to the defense of Johnson, one of the most reviled presidents in American history.

Much more than impeachment connects the presidencies of Andrew Johnson and Donald Trump. No one expected either man to enter the White House. Both presidencies began with a whiff of illegitimacy hanging over them: Johnson’s because he became president when Lincoln was assassinated, Mr. Trump’s because he won the Electoral College despite having nearly three million fewer popular votes than his opponent, the largest losing margin of any president who actually won the election. The size of the gap did not bode well for American democracy.

Historical parallelism rarely works in a simplistic manner. But it does work when historians discern broad similarities and patterns that link our present moment to the past. Many fallible men have inhabited the office of the presidency. Only a handful have been so oblivious to the oath they took that they have met the constitutional standard for impeachment.

The first president against whom impeachment proceedings were considered was John Tyler, who like Johnson became president after an untimely death, that of President William Henry Harrison. A proslavery zealot, Tyler has the unique distinction so far of being the only president to commit treason against his country. He voted for Virginia’s secession from the Union.

Unlike Tyler, Johnson refused to go with his state, Tennessee, when it seceded from the Union. For this, he was appointed military governor of Tennessee and then rewarded with the vice-presidential spot on the National Union Party presidential ticket headed by Lincoln in 1864. Johnson came closest to being removed from the presidency when his conviction fell one vote short of the required two-thirds majority needed in the Senate.