Editor’s Note: The morning after this piece was published, President Donald Trump did precisely what aides were hoping he wouldn't: he tweeted out an insult directed at Cliff Sims, a former aide and author of a new tell all book. The tweet came as Sims was doing a round of cable news interviews. The president's team had been both shocked and impressed with the amount of restraint Trump had shown in not engaging Sims to this point. But, to a person, they knew it could all end at virtually any moment. The end came on Tuesday morning.

During her first White House briefing in 41 days, press secretary Sarah Sanders was asked about a passage in a recently released tell-all book in which top adviser Stephen Miller is quoted disparaging refugees.

What happened next would have been nearly unthinkable in the past two years of the Donald Trump White House.

Sanders didn’t take the bait.

Instead, she spent roughly 10 seconds saying that she wasn’t aware that any such comment—as detailed by former White House aide Cliff Sims in his book Team of Vipers: My 500 Extraordinary Days in the Trump White House—had ever been made. And then she moved on. There was no attack on the author for peddling falsehoods. No extended riff on how pathetic and low-level and uninformed Sims was. It was downright anti-climatic.

Trumpworld is not known for its strategic restraint. If anything the prevailing ethos of the president and his team is that every dig, insult, or mild criticism must be countered with pushback equal parts puerile and churlish. But in the wake of the publication of Sims’ book along with one by former New Jersey governor and onetime presidential transition header Chris Christie, the White House has conspicuously bit its tongue.

The president has not tweeted about either book and the White House has steadfastly declined to comment on the record. For the first time in recent memory, there is a sense of optimism about how the comms shop is handling a news cycle. “If Trump can go the next 24 hours without tweeting about it, the book will be out of the news cycle by this Wednesday,” a former White House official observed.

That’s not to say there’s been no pushback. Plenty has been offered at Sims via anonymous officials with ambiguous titles. Nor is it to say that Trump isn’t tempted to deliver a vitriol-drenched tweet at this former adviser—a friend he used to affectionately refer to as “my Cliff,” according to two people familiar with their past relationship.

According to two Trump administration officials and another source familiar with the situation, the president was furious last week—when he was otherwise supposed to be focused on the government shutdown fight—after he caught wind of pre-release excerpts from Sims’ memoir, which he viewed as confirming media narratives about him and his team being engulfed in tumult, backbiting, and rank pettiness. Two people familiar with the situation said the president stopped using Sims’ name in private conversation over the past week and instead dubbed him a “video kid” whom he hardly even knew. (Politico reported on Monday that Trump had also started dismissively referring to Sims as “the videographer.”)

Trump, the sources added, expressed multiple times last week a strong desire to rage-tweet against Sims, even soliciting advice on what language and put-downs he should use.

Those sources said that senior Trump aides including Jared Kushner (portrayed as a key villain in Christie’s Let Me Finish: Trump, the Kushners, Bannon, New Jersey, and the Power of In-Your-Face Politics) and Kellyanne Conway (portrayed as a key villain in Team of Vipers) successfully counseled the president not to do so, arguing that it would give the situation more attention.

As of Monday evening, the rage has been largely bottled, much to the surprise of those who’ve worked with Trump.

“I have had more convos with people in the White House in the last 36 hours than in the last 36 days. But no one is out there pushing back on the Christie book because it is only critical of Jared and I don’t think Jared cares,” said one former White House aide.

“In Cliff’s book, he goes after everybody, but they’ve stayed quiet. From a PR perspective, I think it is the better move.”

Whether Trump can maintain that silence remains to be seen. The former White House aide was skeptical, especially as both Sims and Christie head off on media blitzes designed to catch Trump’s attention.

The president, the aide recalled, had agreed with his comms team to not engage his former aide Omarosa Manigault Newman, around the time she released her own tell-all, UNHINGED: An Insider's Account of the Trump White House, last year. Ultimately, however, his impulse to attack overwhelmed him and he told reporters and hate-tweeted that the former Apprentice star was a “low-life” and a “dog.”

That pattern has been true with other books too.

Following the release of Michael Wolff’s Fire & Fury early last year, the Trump White House and outside allies united in practically a single voice to lay into the president’s former chief strategist Steve Bannon for his scorched-earth comments to Wolff about the Trump family. Even Trump himself got directly involved, making personal phone calls to top allies, including Republican mega-donor Rebekah Mercer, telling them to sever ties to Bannon and to knife him in the press. After the release of ousted FBI Director James Comey’s book A Higher Loyalty last year, both the White House and Republican National Committee engaged in sustained warfare on Comey’s media blitz, with Trump ordering his press secretary Sarah Huckabee Sanders to play rough with Comey in her press briefing. (“The president wanted her to rip him apart,” one West Wing official told The Daily Beast at the time.)

The tell-all book is a problem every administration encounters, and veterans of past White Houses often argued against engaging at all.

“We often felt like going after books that had factual inaccuracies was important. But breathing a bunch of oxygen into a book that wasn’t going to sell that much meant the press corps was just going to give attention to it for a week because of that,” said Ben LaBolt, a former comms staffer in the Obama White House and the press secretary on his 2012 campaign.

The Trump administration, said LaBolt, “has a credibility problem;” it had become “ the crying wolf shop.”

“Maybe it took years for them to start to learn effective communication strategies,” he added. “But at some point an over-the-top tweet, you realize, doesn’t really do anything valuable.”