WASHINGTON – Sooner or later it was bound to happen. A highly regarded talk show host, widely considered nonpartisan and scrupulously fair, picked up an unverified report from the Internet and used it as fact.

When the subject of the report flatly and justifiably denied it, she had to apologize on the spot.

The incident occurred Wednesday on National Public Radio during an interview with Democratic presidential candidate Sen. Bernie Sanders of Vermont by NPR host Diane Rehm. She started by saying to him: “Senator, you have dual citizenship with Israel.”

Sanders immediately interrupted her: “Well, no, I do not have dual citizenship with Israel. I’m an American. I don’t know where that question came from. I am an American citizen and I have visited Israel on a couple of occasions. No, I’m an American citizen, period.”

The host responded: “I understand from a list we have gotten that you were on that list. Forgive me, if that is….”

Sanders, who is Jewish, snapped back: “That’s some of the nonsense that goes over the Internet. But that is absolutely not true.”

Rehm: “Interesting. Are there members of Congress who do have dual citizenship, or is that part of the fable?”

Sanders: “I honestly don’t know, but I have read that on the Internet. You know, my dad came to this country from Poland at the age of 17 without a nickel in his pocket. He loved this country. … I got offended a little by that comment, and I know it’s been in the Internet. I am obviously an American citizen, and I do not have any dual citizenship.”

The host immediately after her show issued this statement: “I made a mistake. Rather than asking senator and presidential candidate Bernie Sanders whether he had dual U.S./Israeli citizenship as I had read in a comment on Facebook, I stated it as a fact. He corrected me, saying he did not know where that question came from.”

She apologized immediately to Sanders and her listeners “for making an erroneous statement. I am sorry for the mistake,” she said, adding, “However, I am glad to play a role in putting this rumor to rest,” as if somehow taking credit for killing a rumor after passing it on.

The erroneous statement on dual citizenship may have seemed to carry in it the seed of questioning the American loyalty of Sanders, who is Jewish. In the 2008 presidential campaign and thereafter, disproved reports that Barack Obama had not been born in Hawaii similarly clouded his candidacy.

The latest unfortunate episode is a caution for all interviewers and other purveyors of news and commentary on the air or in print.

The NPR host was correct in noting later that had she wanted to raise the question of Sanders having dual citizenship, she should simply have asked him about it.

Relying on Facebook or any other social media, or on unverified input from the public on the Internet, including on the popular site Wikipedia, is a risky evasion of the essential journalistic duty to check the facts of a story before reporting them.

Not only in broadcasting but in print journalism as well, that cardinal rule seems increasingly to be falling by the wayside.

On newspapers struggling against the advertising and circulation losses in the Internet age, copy editors have become a frequent casualty, to the detriment of journalistic quality and reliability.

The widespread intrusion of rumor and gossip mongers into both broadcast and print venues of news and commentary has been a regrettable byproduct of the Internet and social media.

It has come to the point that The Washington Post ran a long piece the other day, complete with an outsized photo, of an acknowledged plagiarist and peddler of assorted Internet chatter who has elevated himself to local media celebrity by essentially waging war on old-shoe, straight-arrow journalism.

The reality is that the Internet, Twitter and all the other social media mechanisms that have broadened the public discourse in our time are here to stay, with new innovations yet to come.

That’s all the more reason for these tools to be used with old-fashioned vigilant regard to accuracy and truth.

Editor’s note: Jules Witcover’s latest book is, “The American Vice Presidency: From Irrelevance to Power,” published by Smithsonian Books. You can respond to this column at juleswitcover@comcast.net.)