Washington(CNN) As he was preparing to remove Jeff Sessions as attorney general, President Donald Trump had already begun reviewing with his lawyers the written answers to questions from special counsel Robert Mueller.

The move to replace Sessions with Matt Whitaker, who has been openly critical of the special counsel, comes as the White House braces for a return of public activity on the Russia investigation following a pre-election quiet period, according to people briefed on the matter.

As acting attorney general, Whitaker also now takes over Deputy Attorney General Rod Rosenstein's role in overseeing the special counsel probe, which officials inside the Justice Department and lawyers representing witnesses believe is moving closer to a conclusion.

Mueller's team has begun writing its final report, multiple sources told CNN.

Before that happens, one of the major questions in the Russia investigation remains to be answered: What happens to Roger Stone, a longtime Trump adviser who has been at the center of a whirlwind of legal activity behind the scenes even during the election-related public quiet period by Mueller.

As recently as a month ago, Mueller asked Trump's lawyers to produce call and visitor logs related to Stone from Trump Tower in New York, according to a source briefed on the matter. The request at this late stage of the investigation came as something of a surprise to lawyers involved, given that the Mueller team has been focused for months on Stone and his activities before the 2016 election.

Among the questions Mueller has asked the President to provide written responses on are queries about Stone and his communications with then-candidate Trump, according to a source briefed on the matter.

Despite the change in leadership at the Justice Department, the Trump legal team believes it won't affect its approach to the Mueller questions, according to one source familiar with the matter.

The President and his lawyers have been aiming to return answers to Mueller's questions later this month, according to one source familiar with the matter. No final decision on an in-person interview has been made.

But Trump's legal team and other lawyers representing witnesses in the investigation expect that the President's responses to Mueller could be one of the final pieces of the 18-month-long probe before the investigators present a report on their findings.

Trump made clear once again in a news conference Wednesday he believes the investigation is a waste of time and money.

"It's a disgrace, it should have never been started because there was no crime," Trump said.

Even after Mueller completes his work, Tuesday's midterm election results mean that House Democrats will also be in a position to expand investigations of Trump. That means Mueller will not be the end of Russia-related questions of Trump and his campaign.

What does Stone have?

The Stone portion of the investigation relates to one of Mueller's central responsibilities: to tell Americans whether there's evidence of collusion between Russians and people associated with the Trump campaign related to the 2016 election.

Investigators have been circling back to Stone's associates they have already interviewed with additional questions. And at least one -- author and well-known conspiracy theorist Jerome Corsi -- is still in discussions about potentially appearing for a second time before the Washington, DC, grand jury that Mueller has been using for the investigation.

Over the last two months, Corsi has been talking to Mueller's investigators "in a really constant basis," he said in a video he posted online on Monday.

RELATED: Roger Stone reveals he talked to Trump campaign about WikiLeaks in 2016

On Thursday, Mueller's team is set to appear in the US Court of Appeals for the District of Columbia Circuit to defend the special counsel's authority as another one of Stone's former associates aims to quash a subpoena for grand jury testimony.

Stone has denied any wrongdoing and has said he didn't have any inside knowledge about plans by WikiLeaks to publish hacked emails from Hillary Clinton's campaign stolen by Russian intelligence in the run-up to the election.

Stone insists he never shared anything about WikiLeaks with then-candidate Trump.

"I never discussed any of this with Donald Trump," Stone told CNN recently. "It's one of the questions that Mr. Mueller wants the President to answer -- one of the written questions. I'm highly confident that his answer will be that he knew nothing about it. We just never discussed it."

On Thursday, Stone told CNN, "I never visited Trump Tower after August of 2015 until the President-elect asked me to visit him after the election." Stone said he visited just one time around late November of 2016 or early December, and that this was his last visit to Trump Tower.

The conversation during that one visit was "mostly congratulatory. It was innocuous. Nothing heavy."

In terms of phone calls in 2016 with Trump, he says they were "occasional and in all cases initiated by him. And we never discussed WikiLeaks."

All signs point to an investigation that is winding down, though Mueller hasn't provided any timeline for completing his work.

Election's impact on Mueller

Even with the Mueller probe seemingly nearing its end, the Russia meddling investigation and its impact is expected to reverberate for months.

The White House is seeking to hire as many as two dozen lawyers for the counsel's office, which will soon by led by Pat Cipollone, following the departure of Don McGahn, sources briefed on the search say. The legal firepower, the President's lawyers believe, will be needed as newly empowered Democrats launch a new round of probes, including pursuing parts of the Trump-Russia matter that Republican leaders had blocked.

One of the important questions the new White House legal team is expected to have to address is whether any of Mueller's findings can be shared with either Congress or the public given executive privilege concerns, which could block release of some or all of Mueller's work.

Under Justice Department regulations, Mueller is required to produce a "confidential report" at the end of his investigation, which includes "the prosecution or declination decisions reached by the Special Counsel."

But the regulations do not require that Mueller's report be released to the public, and with Whitaker taking over, it is not clear whether he will choose to release it at all, or in what form.

One of the sources familiar with the matter said the report will be detailed in part because Mueller's team wants to make sure it withstands public scrutiny. It is expected to include an analysis of the allegations, any information or statements made over the course of voluntary interviews, a legal explanation of why the evidence didn't meet the prosecution bar and an overall defense of the investigation.

How much the Mueller team has accomplished remains a subject of partisan debate. Critics of the President cite guilty pleas from top Trump campaign associates, including former campaign chairman Paul Manafort, and his deputy Rick Gates, as well as Michael Flynn, his first national security adviser.

So far the Mueller team has brought charges against 35 people and entities, secured six guilty pleas, and prison sentences against three people.

Supporters of the President argue that none of the guilty pleas, and the one court conviction, have had anything to do with the Russian interference in the 2016 election, which is what Mueller is supposed to be investigating. The new acting-attorney general has questioned in the past whether there is any obstruction to investigate.

Second-guessing of Mueller

Even inside the Justice Department, there's been second-guessing of some of the Mueller team's work.

One particular focus has the Mueller team's decision earlier this year to include a Russian company among entities and people charged related to operating an internet troll farm that played a central role in Russian interference efforts in 2016.

Some Justice Department lawyers raised concerns about charging the company, for fear it could force the government to share information in discovery that could end up with the Russians.

Those concerns have proven prescient in recent months as the company, Concord Management, hired US lawyers to fight the special counsel in court on a series of fronts. The Concord lawyers have won court permission to access to sensitive information used to bring the charges, though the judge has restricted what can be shared with foreign nationals.

"What a lot of people thought were vulnerabilities in the indictment are now coming to light," said one former Justice Department official.

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The behind-the-scenes doubts were discussed among Justice Department lawyers, some of whom were consulted by the Mueller team before the charges were brought.

A spokesman for the special counsel declined to comment.

Some DOJ lawyers have groused that the Mueller team should have taken a less risky course by focusing the indictment against the Russian nationals, without the companies and entities. That's because since the individuals wouldn't likely respond to the charges and subject themselves to US legal process.

Given the legal fight that has ensued, DOJ will have to handle the upcoming trial in the case and any other legal matters that arise from it, perhaps long after Mueller has wrapped up his inquiry.