Donald Trump’s refusal to commit to accepting the final, official verdict of November’s election has provoked a hue and cry as great as any he has sparked in this long campaign — and that’s saying something. The Republican nominee’s defiance of long-held democratic norms is disturbing, and all the more worrisome because no previous candidate has so consistently and publicly seeded doubts about the presidential election results before the voting even took place.

But Trump’s latest vows aren’t as unprecedented as we keep telling ourselves. While each historical event is unique, we should resist the urge to see Trump as somehow untethered from the American past, as completely unlike all his predecessors. The impulse to cast Trump as a unique threat to the republic has led to a great deal of amnesia and historical airbrushing — creating an idealized picture of a past free of bitterly contested outcomes and crisis. National elections do not always end nicely.

In particular, in their zeal to impugn Trump, some writers have revivedthe myth that Richard Nixon graciously conceded the 1960 presidential election to John F. Kennedy. According to Lyndon Johnson library director Mark Updegrove, Nixon “subordinated his own ambitions for the sake of governmental continuity” and that Trump “would do well to look at” Nixon’s behavior that year.

That’s a hard claim to endorse. The 1960 election between Nixon and Kennedy was a nail-biter. Although JFK seemed to be headed for victory on election night, the outcome wasn’t clear until the next morning. And because of the national vote distribution, Kennedy emerged with an electoral college lead of nearly 100 electoral votes — enough to put his win safely beyond question.

Unlike in 2000, when Vice President Al Gore’s loss to Texas Gov. George W. Bush hinged on a mere handful of ballots in the state of Florida (a state Gore had reason to think he had rightfully won), Nixon had no real basis for believing that a simple recount could remedy enough tallying errors to swing the national results his way. Among the other obstacles he faced, Nixon would have had to reverse Kennedy’s victories in not one but two large states. Still, the narrowness of JFK’s popular margin led angry Republicans to cry that his triumph was fraudulent and to demand investigations. ...