The President has expressed concerns behind closed doors that Mr. Mueller is closing in on his inner circle, including potentially his eldest son.

President Donald Trump said on Friday he had “very easily” answered written questions from special counsel Robert Mueller, though he speculated that the questions had been “tricked up” to try to catch him in a lie. He said he hadn’t submitted his answers to investigators yet.

“You have to always be careful when you answer questions with people that probably have bad intentions,” Mr. Trump told reporters in his latest swipe at the probe into 2016 election interference and possible ties between Moscow and the president’s campaign.

The President did not say when he would turn over the answers to Mr. Mueller, but his attorney, Rudy Giuliani, indicated it could happen next week. The special counsel has signaled a willingness to accept written answers on matters related to collusion with Russia. But Mr. Giuliani has said repeatedly the President would not answer Mueller’s questions on possible obstruction of justice.

During months of back-and-forth negotiations with the special counsel office, Trump’s lawyers have repeatedly counseled the president against sitting down for an in-person interview.

Special counsel Robert Mueller. AP Andrew Harnik

Mr. Trump’s written response, though not yet delivered, signals a new phase in the Mueller probe, the year-and-a-half-long investigation that has produced guilty pleas and convictions from several top Trump aides even as the special counsel and the White House have engaged in lengthy negotiations about how or if the president would testify.

Though he spent hours with his attorneys, Mr. Trump insisted- “My lawyers don’t write answers, I write answers.”

The President’s remarks were fresh evidence of his return to the ominous rhythms of the Russia probe after spending heady weeks enjoying adulation-soaked campaign rallies before the midterm elections.

Despite Mr. Trump’s insistence on Friday that he’s “very happy” with how things are going, his frustrations with the ongoing probe have been evident everywhere from his overheated Twitter feed this week to his private grousing that the special counsel may target his family. Adding to his grim outlook has been the barrage of criticism he’s getting over his choice for acting attorney general and late-arriving election results that have largely been tipping toward House Democrats.

“The inner workings of the Mueller investigation are a total mess,” Mr. Trump tweeted on Thursday as part of a series of morning posts. The investigators don’t care “how many lives they can ruin,” he wrote.

A day later, he tried to put a rosier shine on the situation, telling reporters- “I’m sure it will be just fine.”

The President continued to maintain his innocence while launching new broadsides at the probe. He denied being “agitated” despite his outbursts the day before.

After a relative lull in the run-up to the midterms, the Russia probe has returned to the forefront of Washington conversation and cable news chyrons. There has been widespread media coverage of two Trump allies Roger Stone and Jerome Corsi who say they expect to be charged.

The President has expressed concerns behind closed doors that Mr. Mueller is closing in on his inner circle, including potentially his eldest son.

For months, Mr. Trump has told confidants he fears that Donald Trump Jr., perhaps inadvertently, broke the law by being untruthful with investigators in the aftermath of a June 2016 Trump Tower meeting with a Kremlin-connected lawyer, according to one Republican close to the White House.

Mr. Trump has also complained about efforts in the Senate by his longtime foe, Arizona Sen. Jeff Flake, to introduce legislation to protect the special counsel, according to the officials and Republicans.

Additionally, Mr. Trump has told confidants in recent days that he is deeply frustrated by widespread criticism of his choice of Matthew Whitaker for acting attorney general, according to four officials and Republicans close to the White House who spoke on condition of anonymity. Mr. Whitaker has been a vocal opponent of the special counsel probe.

One argument against Mr. Whitaker was that he has not been confirmed by Senate. Mr. Trump, in turn, contended that the criticism was unfair since Mr. Mueller also was not confirmed for his post. The special counsel position does not require confirmation, and the former FBI director was confirmed for that previous job.

The President also took note of news coverage of his former personal attorney, Michael Cohen, arriving in Washington this week, potentially to meet with Mueller’s investigators. Mr. Cohen has pleaded guilty to a series of crimes and has said under oath that Trump ordered him to make hush-money payments to cover up an affair. He has undertaken an unlikely public relations tour as he looks to make a deal to reduce his prison sentence.

In this Aug. 21, 2018 file photo, Michael Cohen, former personal lawyer to President Donald Trump, leaves federal court after reaching a plea agreement in New York. On Thursday, Sept. 20, 2018, via Twitter, Cohen praised himself for providing critical information? in the special counsel’s investigation into Russian interference in the 2016 election. | Photo Credit: AP

The renewed focus on the looming threat from Mr. Mueller comes as Mr. Trump settles back into the day-to-day routines of governing after the whirlwind campaign in which he spent weeks in front of adoring rally crowds while whipping up his base with harsh rhetoric about migrants moving through Mexico.

On other topics-

Despite his insistence that Americans no longer have to fear North Korea’s nuclear program, news of Pyongyang’s persistent weapons program made headlines this week.

And the White House is hurriedly stepping up efforts to prepare for a series of investigations certain to be launched by Democrats once they take control of the House in January.

Even as Mr. Trump mused in the West Wing about making staffing changes, he pushed back against media coverage of his recent setbacks.

“The White House is running very smoothly and the results for our Nation are obviously very good,” Trump tweeted. “We are the envy of the world. But anytime I even think about making changes, the FAKE NEWS MEDIA goes crazy, always seeking to make us look as bad as possible! Very dishonest!”