Washington (CNN) Robert Mueller's report could land within days, yet rather than offering definitive answers, his hotly anticipated filing might only ignite a new controversy -- over how much of the special counsel's conclusions most Americans get to see.

But the big question is how much of what the special counsel concludes -- after an investigation repeatedly blasted as a "hoax" and a "witch hunt" by the President -- will be made public or even sent to Congress.

Whenever it is filed, Mueller's report will mark a critical point in the Trump presidency, given the gravity of the accusations against his team, and offer the theoretical possibility of conclusive answers about the last White House race.

The reclusive former FBI director's findings could also put the United States on the road to a new and divisive impeachment saga, if he finds collusion with Russia and an attempt by the President to obstruct justice to cover it up.

If there is no case for Trump to answer, Mueller could at least partially lift a cloud that has haunted the White House every day of his presidency, though a flurry of spin-off cases mean the President's legal exposure is far from over.

It will be a fraught political time, since so many Americans have invested so much emotion in the outcome, whether they are liberals who dream of Trump being ousted from power or supporters who buy his claims of a huge "hoax."

Yet key players in Washington and many Americans beyond, transfixed by the barely believable drama leading up to the final report, at least at first, may be let down.

Mueller's endgame is obscured because no one really knows exactly what he will report and the information that Barr will choose -- or feel compelled -- to share with Congress and the public on a scandal that has polarized the nation.

The uncertainty is almost certain to spark a new struggle between Congress, the White House and the Justice Department that could lead to litigation and has every chance of reaching all the way up to the Supreme Court.

Mueller's filing could also herald the reclusive prosecutor's own exit from the stage -- likely after not speaking to the American people from the beginning to the end of his investigation.

That old fashioned reticence, as well as a stellar career in law enforcement, is one reason why Mueller's conclusions will carry such weight -- whether his report is ultimately critical of the President or leaves him in the clear.

What does Mueller know -- and what will he say?

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The special counsel has run one of the most impenetrable Washington investigations in memory. He has, however, sprinkled clues throughout a growing library of indictments and court memos.

While he has yet to openly accuse anyone in Trump's orbit of colluding with the Russians, Mueller has laid out 10 criminal cases, seen four people sentenced to prison, secured one conviction at trial, extracted seven guilty pleas and charged 37 people and entities with crimes.

In richly detailed indictments, Mueller has weaved a tale of Kremlin troll farms, social media campaigns, spear phishing operations and computer hacking.

He's uncovered a pattern of compulsive lying by people close to Trump, often about contacts with Russians, which have raised the key question: What are all of these presidential associates trying to hide?

In one of the most tantalizing unclosed loops, Mueller in recent filings revealed that a senior campaign official was directed by an unnamed person to ask Trump's longtime political adviser Roger Stone about future releases by Wikileaks that could damage Hillary Clinton.

Last week, prosecutors said for the first time they had evidence that Stone -- who is charged with obstruction and witness tampering -- communicated with Wikileaks, which many US analysts believe has links to Russian intelligence.

What kind of report will Mueller file?

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According to Justice Department regulations, Mueller is required to file a confidential report with Barr. It is not clear what form it could take.

One model would be for the special counsel to adopt a traditional, sparse prosecutorial approach to explain the cases he initiated and decisions he made not to charge other people linked to the case.

Barr and Mueller will likely seek to avoid the political furor whipped up by former FBI Director James Comey when he announced he would not charge Clinton after an investigation into her email server but hardily criticized her conduct all the same.

According to the regulations governing his appointment, Mueller is only required to deliver a confidential report to the attorney general outlining why he decided to prosecute some people and declined to pursue others.

Still, a pared down approach would risk coming across as deeply insufficient given the huge political ramifications of the Mueller investigation, which after all, at least indirectly centers of the behavior of a sitting President.

Given his by-the-book history, it's likely that Mueller would follow the prevailing Justice Department opinion that a sitting President cannot be charged in a criminal case, even if he has evidence that Trump transgressed in some way.

So he could choose to include information about Trump's conduct in his report that he believes should be sent to Congress -- the sole constitutional authority for judging presidential wrongdoing.

But since so much of Mueller's work is a mystery, no one outside his tight operation can say for sure exactly what he might do.

Barr's dilemma

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Once Mueller files, the focus shifts to Barr, who will come under immediate pressure from Democrats in Congress to allow maximum public access to the special counsel's conclusions.

"The attorney general, as I understand the rules, would report to Congress about the conclusion of the investigation," Barr said in his Senate confirmation hearing last month.

"I believe there may be discretion there about what the attorney general can put in that report," he said.

His comments prompted concern among Democrats and raised the possibility that, at least initially, the evidence and reasoning that led to Mueller's final conclusions may be kept under wraps.

"I think the American people deserve to know the truth. As Thomas Jefferson used to say, 'if the people know the truth, they won't make a mistake,'" Sen. Tom Carper, D-Delaware, told CNN on Wednesday.

Barr could be constrained in his report by the need to respect grand jury secrecy rules, a desire to protect classified material and sources and methods and the reputations of people interviewed by prosecutors and not charged.

Trump's lawyers have already indicated they may seek to have parts of the report withheld through assertions of executive privilege. Such comments have provoked fears that there could be an effort by the administration to use legitimate legal considerations to withhold information that could be damaging to the President.

Democrats, especially Democratic Rep. Jerrold Nadler, chairman of the House Judiciary Committee, are preparing to act if there is any such blocking maneuver.

Barr also knows there will be strong desire among the public to release details about an investigation that has overshadowed Washington politics and the result of the 2016 election for two years and cost millions of dollars.

On the flip side, Barr will be under fearsome pressure from Trump, who has turned on senior law enforcement officials who he feels have offered him insufficient protection.

House Democrats have subpoena power that they may use either to try to force the release of Mueller's full report, or get evidence and testimony uncovered by the special counsel and not released to Congress.

All of this could set the stage for a massive legal battle and yet another clash between the executive and legislative branches of the US government.

"Barr isn't going to have the final say here," said Susan Hennessey, a former National Security Agency attorney who is now a CNN legal analyst.

"If he tries to withhold even one word of the Mueller report from Congress, they are going to litigate this question to the absolute end of the earth," Hennessey told CNN's Wolf Blitzer on "The Situation Room."

"They are really, really going to push the executive privilege issues. It is almost certainly going to wind up in the United States Supreme Court," she said.

Only the beginning

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Just because Mueller may be finishing up, it does not mean the end of Trump's legal exposure -- nowhere close.

To begin with, elements of Mueller's report and evidence and source information he uncovered could provide fuel for an accelerating Democratic investigation into Trump's links with Russia.

At some point, Democratic leaders may face a choice, if Mueller and Barr indicate that there was wrongdoing by Trump, whether to initiate impeachment proceedings with all the nightmare political consequences that such a step would entail.

Mueller's team has farmed out various cases, not seen under his direct jurisdiction, to prosecutors elsewhere, including in New York.

The President's campaign, transition and administration are currently the subject of a string of civil and criminal legal probes.

Many analysts believe that investigations being pursued by the US Attorney's Office for the Southern District of New York that are now delving deep into Trump's business empire could ultimately prove the most damaging legal threat to the President.

That means the final shots of the Mueller investigation may only be the end of the beginning of the legal and political nightmare the President will endure.