Yet on March 31, 1968, Johnson announced that he would not seek a second term because, as he put it on prime-time television, “There is division in the American house now.” Do not expect any such capitulation from Donald Trump. Division in the American house is precisely what gives him a shot at four more years.

Unlike in 1968, in other words, urban unrest with a racial dimension might actually save a beleaguered incumbent. The current wave of protests is in many ways a repeat of more recent events — Ferguson 2014, Charlottesville 2017 — and its main significance may be to shift the American political conversation away from the Trump administration’s incompetent handling of the Covid-19 pandemic, back to the terrain of the culture war, where Trump is an experienced combatant.

Even in 1968, merely using the phrase “law and order” was to invite accusations of racism. In the case of a president who last week fantasized about a MAGA mob joining the fray outside the White House, the charge of insincerity seems well-founded. Trump is indifferent to the law by nature; he thrives on disorder. And he understands much better than his opponent how to spread his message through the complex networks of online “influencers” — many of whom promote conspiracy theories — through which more and more Americans receive their news.