But these irregularities do not add up to a stolen election in multiple states. Even if Mr. Biden’s narrow victory was overturned in one of the closely contested states, he would have more than 270 electoral votes. John Kerry and Al Gore both would have won had they not narrrowly lost Ohio and Florida, respectively, but they both conceded (Mr. Gore after a long legal fight). Richard Nixon conceded in 1960 despite evidence that he was cheated out of Illinois. All did so at least in part to avoid tipping the U.S. into irreparable political division.

There’s no predicting how Mr. Trump will behave. He rarely takes our advice—we said in January 2017 that he should fire James Comey upon taking office—and perhaps he will continue his “stolen” election claims past Jan. 20. Perhaps he can’t admit to himself that he lost. Perhaps he hopes to nurture resentment to run again in 2024.

But bitterness as a political strategy rarely wears well. If Republicans lose the Georgia Senate runoffs on Jan. 5, Mr. Trump will deserve much of the blame. If election protests turn to violence in the streets, as they did on the weekend in Washington, he will be blamed whether he deserves it or not. Mrs. Clinton’s example of still claiming she was cheated, four years later, hasn’t enhanced her reputation.

There’s a time to fight, and a time to concede.