With a tap of the thumb, President Trump on Friday invited speculation that he or a family member could be indicted by a federal grand jury whose existence was reported a day earlier by the Wall Street Journal.

The president retweeted a video clip from the “Fox & Friends” morning show, his favorite, in which the hosts and guest Jeanine Pirro — “Judge Jeanine” on Fox and a longtime Trump friend — cast an investigation of possible coordination between Russia and the Trump campaign, led by special counsel Robert S. Mueller III, as a politically motivated witch hunt.

That the president would endorse such a view is unsurprising, but it seemed odd that he would call the attention of his 35 million followers to what came next — a discussion of indictments.

“This is an agenda,” Pirro said, “and my concern is if they end up with an indictment against a family member just to, you know, just to get at Donald Trump when they couldn't get at him, there's going to be real uproar, a real uprising in this country.”

“Who says they can't get at him?” replied host Brian Kilmeade.

“Look, I was a prosecutor for 32 years,” Pirro answered. “You can indict a ham sandwich.”

The clear implication was that indictments against Trump or a family member would be unjustified. Yet “Fox & Friends” presented them as real possibilities.

Why would the president voluntarily lend credence to that notion?

It is too early to gauge the likelihood that a grand jury impaneled in Washington several weeks ago as part of Mueller's investigation will indict anyone. “Fox & Friends” was just doing what cable news shows do — looking ahead to one possible outcome and filling airtime by chatting about it. In this case, the Trump-friendly program's goal was to preemptively delegitimize any indictment that might be handed down.

That makes sense for TV talkers, but for Trump to entertain the prospect of an indictment is an unforced error that plants questions about whether he has any reason to think an indictment might be coming. A more prudent strategy would be to project confidence that he has nothing to worry about because he did nothing wrong.

Trump's retweet also is striking in the context of reports that his new chief of staff, John F. Kelly, is trying to help him steer clear of trouble by restricting the information that reaches the president. A front-page story in Friday's New York Times put it like this:

Mr. Kelly, 67, has told his new employees that he was hired to manage the staff, not the president. He will not try to change Mr. Trump’s Twitter or TV-watching habits. But he has also said he wants to closely monitor the information the president consumes, quickly counter dubious news stories with verified facts, and limit the posse of people urging Mr. Trump to tweet something they feel passionately about.

It appears that Kelly has a sober grasp of his limitations — which were on full display hours after the Times published its report, as Trump tweeted something he saw on TV.

The question is whether Kelly's managerial discipline can make up for the things (or the thumbs) he can't control.