Donald J. Trump’s refusal to agree to accept the results of the election in the event he loses — which now seems more probable than ever — raises historic concerns about where we might be headed once all the ballots are counted.

The Republican presidential nominee would not commit to accepting the outcome while responding to a question from debate moderator Chris Wallace. He’ll “look at it” when the moment comes, Trump said.

Trump is now on the cusp of losing the presidency to Democratic nominee Hillary Rodham Clinton. We’ve had a long and well-established — and wisely admired — tradition in this country of losing presidential candidates accepting these results with grace and class.

Peaceful transition of presidential power begins right there.

Trump won’t promise to do that.

Oh, I can hear my friends on the right now griping about the “precedent” set in 2000 when Democratic nominee Al Gore refused to concede the election to Texas Gov. George W. Bush.

The immediate aftermath of that vote count was swathed in tension and controversy. The results from Florida weren’t yet known. That state’s electoral votes would be decisive in determining the next president. Gore conceded, then took it back once it became evident that another authority needed to step in; that would be the U.S. Supreme Court.

Well, the court ruled 5-4 that the Florida ballot recount should stop and that Bush would finish with 537 more votes in that state than Gore. Bush won the state — and was elected president.

What did Gore do? He conceded again — for the final time — and in the process brought some humor into the event by agreeing that “this time” he wouldn’t take it back.

He offered his full support to the new president.

So, let’s get off this idiotic notion that Al Gore did what Trump might do on Election Night.

Donald Trump is hinting that he might not accept the results no matter how wide the margin. In the process, Trump is feeding a dangerous — and demonstrably false — narrative about “rigged” and “phony” election results.