Washington (CNN) Robert Mueller's latest service to America is all but complete. But the reverberations from his yet-to-be-revealed report could amount to inestimable political and constitutional consequences.

The conclusion of the special counsel's investigation was an important landmark in itself, at a moment in America's modern history when governing institutions are under intense strain. It demonstrated that so far at least, a credible legal examination is possible into the most explosive of charges against an unchained President, without interference and despite the bitter polarization of the times.

The question now is whether everyone accepts the result.

The nation could learn within days whether Mueller answered key inquiries : Did Trump cooperate with a hostile foreign power to win the 2016 election? Did he use that platform to seek to enrich himself with multi-billion dollar business deals in Russia? Did the President obstruct justice, including by firing FBI Director James Comey, in an effort to cover it all up? And is there any evidence to suggest why Trump often appears to be obedient to Russian President Vladimir Putin, following fears felt deep within the FBI that the US President was compromised? And can he explain the multiple suspicions contacts between Trump's associates and Russians -- both before and after the election -- and the lies they all told about those relationships?

Trump's team is already celebrating, claiming it is already clear that the President has already been vindicated since Mueller did not indict anyone for cooperating with Russian election meddling.

The lack of charges against Trump's son, Donald Jr. and his son-in-law Jared Kushner, who were involved in a 2016 Trump Tower meeting with Russians offering "dirt" on Hillary Clinton, especially disappointed his critics.

Their escape proved the shrewdness of Trump's consistent messaging that the only question that mattered in an investigation that held Washington spellbound for two years was whether there was collusion.

"The fat lady has sung," one Trump aide told CNN's Jim Acosta.

For now, consistent with Mueller's tightly controlled investigation, no one outside the Justice Department knows what is in the report, how long it is and how much it deals with the President's own actions.

But its delivery sets up an even bigger test for Washington's political institutions than those involved in getting it safely to its culmination.

So much political and emotional capital has been invested in Mueller's probe by partisans on all sides that it's already clear that it will not mark a moment of catharsis that will once and for all drain the bitter poison of the 2016 election.

Mueller is sure to anger millions of Americans who do not find validation for their set-in-stone political convictions in an assessment that could conceivably dictate the fate of the Trump presidency.

The choices made in the coming days and the revelations to come are likely to ensure that whatever Mueller's report says, the question of Russia's assault on the last presidential election will stain the next one in 20 months.

Attorney General William Barr, a pillar of the legal establishment, weeks into his second spell in the job, now assumes the crucial historic role of deciding how much of the report the White House will initially see, and the extent to which Mueller's conclusions will be shared with Congress and the public.

Still, even if there is not legal liability for the President or his family in the Mueller report, it could still inflict significant political damage.

Peril still lurks for Trump

The biggest peril for Trump always lay in the obstruction question and whether there was conduct on his part that Mueller could not charge in deference to the tradition that a sitting President can't be indicted.

Democrats wasted little time in demanding the full and swift release of Mueller's entire report, seeking the evidentiary haul behind to power their own investigations.

But they have a sensitive set of decisions as well. If the report in any way vindicates Trump, Democrats could endanger their new House majority by continuing to pursue him aggressively.

Republicans will argue that if Mueller, a decorated former Marine and ultimate Washington straight arrow, clears Trump, a new flurry of investigations would amount to presidential persecution.

However the political battle shapes up, it's important to realize that the Mueller probe -- though it has dominated Washington's attention for nearly two years -- is only one piece of the legal puzzle gathering around Trump.

It is unclear how much evidence Mueller can present on the question of contacts between Russians and people in Trump's orbit since the counter-intelligence side of the investigation -- which could still be going on at the FBI -- involves classified information, sources and methods.

There are also multiple criminal and civil cases threatening Trump, his businesses, his inaugural committee and his presidential transition. The most perilous appears to be one launched by the US attorney's office in the Southern District of New York that has already implicated Trump in campaign finance offenses over hush money payments made to women who alleged affairs with him before the election.

Then there are multiple investigations launched by Democratic House committees that if they do not result in grounds or the political motivation for an impeachment drive, could be used to make a case against Trump to lay before voters in 2020.

Where do Barr and Mueller go from here?

Barr spent several hours reading the Mueller report in his office after the special counsel handed it over just before 5 p.m. ET on Friday afternoon.

Now he must decide whether there are sufficient grounds to share parts of it with White House lawyers in anticipation of executive privilege assertions -- a move that could give Trump and his team the chance to mount a pre-emptive defense.

In a surprise, a Justice Department official said that Barr could brief lawmakers on his takeaways from the Mueller report as soon as this weekend. That means that the crucial answers from Mueller's investigation could emerge publicly more quickly than expected.

Still, a constitutional showdown still seems likely. Evidence gathered by Mueller about the firing of Comey, the President's conversations about Russia with his fired national security adviser Mike Flynn and his conversations with aides about the Trump Tower meeting once he was President could all be subject to executive privilege assertions.

Democrats with subpoena battle could then launch a court battle that could drag on for months.

And Democrats are already threatening action if the whole of the report, and all of its supporting evidence is not quickly released. They also may call on the special counsel to explain himself in person.

"I think the American people need to hear from Mr. Mueller," said California Democratic Rep. Eric Swalwell, who sits on the House Intelligence Committee, on CNN.

One of the difficulties in assessing how the Mueller drama will unfold from here is that the structure of his report remains unclear -- even though a Justice Department official described it as "comprehensive."

Will he, for instance, confine himself to an examination of criminal matters -- and a explanation of the charges he laid against 37 people and entities, including associates of Trump like former campaign chairman Paul Manafort and Trump's ex-attorney Michael Cohen and his reasons for not charging other key players?

Or has the special counsel told a story of political offenses committed by the President and his team, that could be potentially relevant to the question of impeachment?

How has he dealt with the intense public interest in his investigation and the President's conduct -- and the wider mission of uncovering and explaining an attempt by Russian intelligence agencies to sway the 2016 election to Trump?

How Trump will spin the outcome

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It must have come as a huge relief for the President that no one in his immediate family was indicted and Mueller did not lay charges on the question of conspiracy to collude with Russia to interfere in the election.

There have been plenty of dark days for the President during the Russia investigation. But the news that Mueller would make no more indictments arrived as he settled into his Mar-a-Lago resort for a weekend with friends -- surrounded by his legal and political teams.

One person close to Trump told CNN's Pamela Brown that "we won" and that the campaign -- which has been tainted for two years by the suggestion of wrongdoing -- was absolved.

"Zero indictments mean we're clear," the person said.

Trump's legal team can also claim a victory since they were able to protect their client by not permitting him to sit for an interview under oath with Mueller -- a situation that could have exposed the President to the possibility of perjury. The President did provide answers to written questions filed by Mueller, with the help of his counsel.

Still, the President's team faces nervous hours until they can learn the entirety of the report.

Whether Mueller finds a pattern of repeated obstruction by the President remains a mystery. It's also possible that the special counsel outlines a pattern of behavior related to Russia, that if known by voters before November 2016, would have appeared deeply unpatriotic and made it impossible for him to win the presidency.

While there was a mood of celebration in the Trump camp on Friday night -- things could quickly change.

The President has made clear that if Mueller delivers a result favorable to him, he will see the report as accurate and fair. Despite months of angry tweets and comments insulting Mueller and his team, the President is likely to quickly pivot to using the special counsel's sterling reputation to his own advantage.

But if he is criticized in the report, it will validate in his own mind, the endless claims that the whole exercise was a "witch hunt" all along.

The President's legal team has gamed out a range of strategies to cope with a report that is highly critical of Trump, that is mixed, or offers him a measure of validation, CNN has reported.

Democrats face a choice

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Indications that Barr may be able to brief lawmakers soon about the report sparked immediate speculation, alongside the lack of new indictments, that the Mueller report could be more favorable to the President than expected.

Democrats appeared to be preparing for that possibility by stressing that the report was just the beginning of a new phase of the Russia intrigue.

In a statement, House Speaker Nancy Pelosi and the top Senate Democrat, Chuck Schumer, warned that Barr should not give the White House a "sneak preview" of the report.

In an apparently coordinated messaging blitz, key Democratic leaders and presidential candidates issued statements demanding the immediate public release of Mueller's entire report and evidence backing it up.

Such a trove would be valuable for the multiple House committees that are delving into almost every aspect of Trump's business and political affairs.

House Intelligence Committee Chairman Adam Schiff made clear that his investigation would look at questions that may not be covered by Mueller, including why Manafort gave polling data to a Russian contact with links to Kremlin intelligence agencies. He also pledged to look at whether Trump was compromised by his business or other links with Russia from before he became President.

"If they are not answered, we are going to have to answer them," Schiff told CNN's Wolf Blitzer.

His comments showed that while Mueller's decision to file a report and end his investigation was a milestone moment, it was also the start of a new beginning of the Russia saga.