Republican presidential nominee Donald Trump told supporters in Columbus, Ohio, Aug. 1 that he worries the Nov. 8 election "is going to be rigged." (The Washington Post)

Republican presidential nominee Donald Trump told supporters in Columbus, Ohio, Aug. 1 that he worries the Nov. 8 election "is going to be rigged." (The Washington Post)

Of all the dangerous things Donald Trump has said, perhaps the most concerning is his assertion that the election might be rigged. This irresponsible, unsupported suggestion augurs poorly for Trump’s behavior in the increasingly likely event of his loss.

“The election’s going to be rigged,” Trump warned at a rally in Ohio. “I’m telling you, November 8, we’d better be careful, because that election is going to be rigged,” he told Fox News’s Sean Hannity.

Those comments set the stage for an explosive outcome the likes of which this country has never seen. It is not far-fetched to imagine Trump inciting his partisans against accepting the verdict of voters, further inflaming an already toxic political climate in Washington.

As much as Republicans sought to ensure President Obama’s failure from the moment of his election, their animus toward a President Hillary Clinton would be that much greater — even without Trump piling on. Clinton would enter office as a more divisive figure; after all, the GOP argument that she is disqualified to hold the office, whether by virtue of Benghazi or emails, preceded Trump’s “Crooked Hillary” attack.

If Clinton is elected, Republicans will have been shut out of the White House for three elections in a row, for the first time since 1948. And if Democrats retake control of the Senate, Republicans eyeing the 2018 map — when 25 Democrats (and independents caucusing with Democrats) and only eight Republicans face reelection — would have every incentive to impede Clinton’s initiatives. They would try to make her not just a one-term president but a two-year one.

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Add to this predictable ugliness a losing nominee who rouses supporters with assertions that the election was somehow stolen from him and you have a recipe for turmoil of a most un-American variety.

Just how un-American can be judged by looking to Al Gore’s gracious concession to George W. Bush. The Democratic nominee had won the popular vote; he had every reason to believe that, but for a botched election and a butterfly ballot in Florida, he would have won the electoral college majority as well.

Nonetheless, Gore, in the aftermath of the Supreme Court’s ruling, spoke of meeting with Bush “so that we can start to heal the divisions of the campaign and the contest through which we’ve just passed.” He invoked Sen. Stephen Douglas on being defeated by Abraham Lincoln — “Partisan feeling must yield to patriotism” — and added, “This is America, and we put country before party. We will stand together behind our new president.”

There is every reason, from his current comments and his history, to think that Trump would respond in a different, far less elevated manner. Consider Trump 2012, who unleashed a stream of unhinged tweeting about Mitt Romney’s loss — unearthed by my Post colleague Stephen Stromberg.

The president “lost the popular vote by a lot and won the election. We should have a revolution in this country,” Trump proclaimed, although Obama in fact won both the popular vote and the electoral college. A few minutes later: “The phoney [sic] electoral college made a laughing stock out of our nation. The loser one!” A few minutes later: “We should march on Washington and stop this travesty.”

Trump notwithstanding, the election was not “a total sham.” The electoral college, for better or worse, is specified in the Constitution. Calling for revolution? Imagine what Trump might do when the loser is himself.

In his interview this week with The Post’s Philip Rucker, Trump offered an unsettling preview. The United States, Rucker noted, has a tradition in which losers “concede graciously and try to get their supporters on board like Al Gore did in 2000. Would you?”

Trump: “I don’t want to jump the gun. I don’t want to talk about that. I’m just saying that I wouldn’t be surprised if the election . . . there’s a lot of dirty pool played at the election, meaning the election is rigged.”

Trump’s evidence, such as it is, of prospective rigging involves the string of recent court rulings invalidating voter-ID laws and the phantom menace of voter fraud. “The voter ID situation has turned out to be a very unfair development,” Trump claimed to Rucker. “We may have people vote 10 times.”

There is no such evidence. The provisions of North Carolina’s restrictive voting law, a federal appeals court just ruled, “impose cures for problems that did not exist.”

Trump is dangerous, and the threat he poses might not be extinguished by a loss at the polls.

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