Inevitably, Trump would soon return to form. We don’t often hear either of those rhetorical devices invoked anymore. The beginning of the end was when Trump initially condemned the white-supremacist rally in Charlottesville, Virginia, that ended with the murder of the counterprotester Heather Heyer, and then turned around and insisted that there were “some very fine people” on both sides. Despite Trump’s initial condemnation, white nationalists were left convinced that the president, whatever his aides might persuade him to say publicly, was sympathetic to their movement.

This all established a clear pattern: Fake Trump is magnanimous; Real Trump is petty. Fake Trump represents all Americans; Real Trump cares only about his base.

The problem is not, as some have suggested, an eroding standard of civility in political discourse. Even early in the republic, politics at the presidential level were often nasty. But there is a distinction between speech that is mean, objectionable, or even false and speech that explicitly justifies violence. In a democracy, civility is optional. Nonviolence is essential. Which is why American presidents must genuinely condemn political violence against their opponents.

Adam Serwer: Trump hits the panic button.

That is what makes Trump’s frequent, obvious insincerity dangerous, because there are times when the president must be trusted. On Friday, Cesar Sayoc, a 56-year-old Florida Republican, was arrested for sending explosive devices to Democratic leaders and prominent Trump critics, including CNN. For the past week, the president has issued the rote condemnations of political violence that one would expect from a U.S. president. The problem is that there’s no reason to believe he means a word of it.

As my colleague David Frum writes, Trump has not made any gestures of sympathy toward those targeted. Instead, he has framed himself as the true victim of an attempt to assassinate leaders of the opposition party and suggested that the anger that led to the bombs was the result of the media being too critical of him. Last week, the president praised a congressman who, in an act of utter cowardice, physically attacked a reporter who asked him a question; at other times, the president has encouraged his supporters to attack anti-Trump protesters by offering to pay their legal bills. In the meantime, the Republican Party has been running ads accusing Democrats of encouraging violence, even as the president does just that publicly, a gambit some in the media have rewarded by suggesting that left-wing protesters heckling politicians in restaurants is a kind of violence.

An irony of this discourse is that conservative Trump defenders, and some in the media, have adopted a version of the oft-parodied argument among some on the left that words can constitute violence: Left-wing words are violence, and right-wing violence is just words.