Newsweek reporter Kurt Eichenwald on "Good Morning America." ABC Newsweek reporter Kurt Eichenwald said Tuesday that his baseless claim that President-elect Donald Trump was once institutionalized in a mental hospital was actually part of a series of jokes and intended to be a "signal to a source" to talk to him.

Eichenwald's explanation came Tuesday on "Good Morning America," as host George Stephanopoulos asked him about the September tweet in which he said, without evidence, he believed "Trump was institutionalized in a mental hospital for a nervous breakdown in 1990."

"Any regrets about that?" Stephanopoulos asked.

"There's a long story behind it," Eichenwald said after some brief laughter. "When you go through the full lead-up to that tweet — there was a reporting purpose for that tweet going out, which is more than you are going to want to hear about.

"I was making fun of Fox News and the rest, who were doing 'Hillary has seizures,' 'Hillary has multiple sclerosis,' 'Hillary has Parkinson's,' you know, let's go to Dr. Oz," he continued, referring to a point in the election during which the two major-party presidential nominees' health was under the microscope.

"So I was writing a series of jokes leading up to that with the intent of sending that tweet, which was a signal to a source to talk to me," Eichenwald concluded.

That explanation went unchallenged by Stephanopoulos, who moved on to another topic.

Making a false charge against a presidential candidate on a public platform the way Eichenwald suggested he did would represent a sharp break from traditional journalism ethics.

In an interview last week, Eichenwald struggled under repeated questioning from Fox News host Tucker Carlson to explain his outlandish mental-hospital claim.

Eichenwald has also been in the news in the past week after he vowed to press charges against an anonymous Twitter user who sent him a flashing GIF, which Eichenwald said caused him to have a seizure.

A representative for Newsweek did not immediately respond to a request for comment.

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