Then-FBI Director Robert S. Mueller III in 2012. (Jim Lo Scalzo/EPA-EFE/Shutterstock)

The delivery of special counsel Robert S. Mueller III’s report to Attorney General William P. Barr signaled the end of one phase of the long investigation and the beginning of another. What was primarily legal with political overtones now becomes an all-out political battle that ultimately will shape, and perhaps decide, the 2020 presidential election.

Legal proceedings — investigations and trials — will continue, in courtrooms in New York and Virginia and Washington, as aspects of Mueller’s investigation that were handed to other prosecutors continue to move forward. They threaten various aspects of President Trump’s empire, including his business, his foundation and his inaugural committee. The combined efforts of Mueller and others already have ensnared, with indictments or pleas or convictions, Trump’s former campaign chairman, his longtime legal fixer, his former national security adviser and a confidant who long has been a practitioner of the dark arts of politics.

Those ongoing investigations will be a constant for some time. They will produce headlines and fodder for cable news programs, just as the pieces of Mueller’s investigation created sensational revelations over the 675 days of its life. The indictments, convictions, guilty pleas, as well as the documented information about Russian interference in 2016 that Mueller and his team produced, underscore the seriousness and validity of an investigation, regardless of Trump’s claim that it was a “witch hunt.”

The initial headline coming out of the delivery of the report Friday, which was that Mueller plans no further indictment, was interpreted as very good news for the president, who had turned his “no collusion, no collusion” mantra into presidential walk-up music when he greeted reporters Friday morning on the White House South Lawn. The nearer the report was, the more he escalated his rhetoric about it.

Now, if the report’s conclusions and full details recommend no further jeopardy for the president, he will claim a victory — over the Democrats, the media and all his other critics. That is a big if, however, given that the contents remain secret — which is why at this moment, as with earlier stages of the Mueller investigation, what isn’t known is as important as what is known.

What’s known already is quite extraordinary, whether in terms of efforts by Russian intelligence to disrupt and influence the 2016 presidential election or in the number of contacts between associates of the Trump campaign and Russians. To some eyes, what happened adds up to collusion. Yet Mueller’s legal team ended its investigation without charging anyone with conspiracy against the United States. That will give the president his principal talking point from here forward, regardless of other questions about hush money, business overtures to the Russians and the like.

Whether Mueller’s report says anything definitive about obstruction of justice is another question. Trump has been open about his efforts to affect and diminish the investigation, whether through the firing of FBI Director James B. Comey, belittling Mueller and former attorney general Jeff Sessions, trying to get the Justice Department to go easy on former national security adviser Michael Flynn (who pleaded guilty to lying) or hints of pardons for those caught in Mueller’s net.

Did Trump fear the investigation because he had something to hide, or did he simply find it a terrible nuisance that was shadowing his ability to do other things?

Mueller has done his job. Now it will be left to others to digest, analyze and interpret that work. What comes next may lie in the hands of Congress, at the start principally House Democratic leaders: Speaker Nancy Pelosi (D-Calif.) and the chairs of the Judiciary, Oversight and Intelligence committees.

Senate Minority Leader Charles E. Schumer (D-N.Y.) and House Speaker Nancy Pelosi (D-Calif.) in January. (Saul Loeb/AFP/Getty Images)

There are two tracks pitting Congress against the White House. The first was set in motion earlier. The House Judiciary Committee sent requests for documents to scores of people and entities. The Oversight Committee has asked the White House for a mountain of documents. The Intelligence Committee has been at work for nearly two years, though only now under Democratic control.

So far, the White House has been generally uncooperative. There is no reason to expect that to change. There will be many months of jousting ahead.

The second and now immediate track will be the one launched Friday, the demand by Democratic leaders that Barr release the full Mueller report and all the underlying documentation. Barr promised Friday “as much transparency as possible,” with the caveat that he would consult with Mueller and Deputy Attorney General Rod J. Rosenstein about what could be released “consistent with the law.”

Pelosi already has set a high bar for impeachment: She is opposed unless there is evidence that is “so compelling and overwhelming and bipartisan” that it justifies that huge step. Without the Mueller report as a foundation, it will be difficult for Democrats in the House to meet that standard. That doesn’t mean they won’t be under pressure from their base to push in that direction.

When the House impeached President Bill Clinton in December 1998, it was on the basis of the report from independent counsel Ken Starr delivered just three months earlier. The Judiciary Committee at that time conducted no investigation of its own.

It remains to be seen whether the Mueller report contains information compelling enough to warrant impeachment proceedings. House Democrats soon could face difficult questions about whether and how to target or limit the scope of their investigations of the Trump administration. They have the responsibility for oversight, but already they were being questioned about potential overreach in the ambitions of their investigations. They could face harder questions, depending on what the Mueller report shows.

These are political questions and political judgments. House Democratic leaders must decide what to do once they know the full contents of the Mueller report; the sooner that report is publicly released, the better for all involved. Republicans will have their own questions to answer, again depending on what is in the report, in part because the absence of evidence of collusion alone is not a full exoneration of the behavior of the president.

Right now, the Mueller investigation animates parts of the Democratic base and parts of Trump’s base. For most people, however, it has been background noise — too complicated to follow closely and exhausting, as is so much with the Trump presidency.

Ultimately, however, it will be in the public’s hands. All of it — the information already known, the Mueller report, the ongoing legal cases, the investigations by House Democrats and the actions of the president — will go to the public for the ultimate verdict. That will come in November 2020. By then, no one will lack for information to make a judgment.