Robert S. Mueller III on Oct. 28, 2013, in Washington. (Charles Dharapak/AP)

It appears that special counsel Robert S. Mueller III is close to wrapping up his investigation of whether Donald Trump’s 2016 presidential campaign coordinated with Russia’s effort to interfere in that year’s election. More than 80 percent of Americans want Mueller’s report made public in its entirety, according to a recent Washington Post-Schar School poll, but the conclusion of Mueller’s investigation is poised to be disappointing. The administration, in the form of Attorney General William P. Barr, has primary control over what information is released.

The Post’s Aaron Blake walked through four big questions about the conclusion of Mueller’s effort, including what Americans might end up seeing of the final report given to Barr. But it’s worth picking out some of the questions that the report might answer, questions we know exist and to which we’d like answers.

The list below is not comprehensive, certainly, largely ignoring the ancillary questions involving possible obstruction of justice or incidents that occurred after the election. It focuses, instead, on Mueller’s primary mandate: digging up whatever evidence of coordination might exist.

Did Paul Manafort’s interactions with Konstantin Kilimnik demonstrate coordination? On Aug. 2, 2016, shortly after the FBI had opened its investigation of the Trump campaign and a little more than a week after WikiLeaks had begun dumping files stolen from the Democratic National Committee, Trump’s then-campaign chairman, Paul Manafort, and deputy Rick Gates had dinner at a private club with a former colleague named Konstantin Kilimnik. Kilimnik, a Russian, worked with Manafort and Gates while they consulted for a Ukrainian political party sympathetic to Russia. Kilimnik is also thought to have ties to Russian intelligence.

At that meeting, it’s possible that Manafort and Gates provided Kilimnik with polling data from the Trump campaign. (Trump’s campaign pollster, Tony Fabrizio — also a longtime partner of Manafort’s — was interviewed by the Mueller team last year.) It’s an interaction that has emerged as one of the most fertile grounds for theories of coordination with Russia, powered in part by comments from one of Mueller’s lawyers during a hearing focused on Manafort in which he said that the meeting gets “very much to the heart of what the Special Counsel’s Office is investigating.”

How close to the heart did it get? Was Manafort acting as an agent of the campaign hoping to provide information to Kilimnik that Russia would find useful in its interference efforts? Or was Manafort trying to leverage his position with the campaign for his own financial benefit?

Why didn’t Mueller interview Donald Trump Jr.? At no point, it seems, did Mueller’s team interview Donald Trump Jr., seemingly someone central to the investigation, given his role in the campaign broadly and in interactions with Russians before and during the meeting at Trump Tower in June 2016.

When we noted last year that Trump Jr. hadn’t been interviewed, Elizabeth de la Vega, a former federal prosecutor, offered one possible explanation for that gap: that Trump Jr. “is a serious subject or, quite possibly, a target of the special counsel investigation.”

“Federal prosecutors rarely interview targets of an investigation,” she said. “Instead, they build the case around them, with documents, emails, public admissions and other witnesses.” At one point last year, Politico reported that Trump Jr. expected to be indicted.

The Trump Tower meeting itself may have violated federal law, according to former White House counsel Bob Bauer.

“The Trump campaign invited them to come,” he said, referring to the offer of a meeting with a Kremlin-linked lawyer who, it was suggested, had dirt on Democratic presidential candidate Hillary Clinton. “It was a proposition that was offered, and it was accepted.”

“The law prohibits Americans from soliciting foreign nationals’ assistance,” Bauer continued. “The solicitation provision is very broad. You don’t have to specifically say, ‘I really would like you to do X’; you could indicate, since they’ve already said they want to help you out, that you’re open for business. That you actually want their support.”

Did Trump know about the Trump Tower meeting? Part of what Trump Jr. might help inform is whether his father knew about the Trump Tower meeting in advance, something that he has repeatedly denied. If Trump knew, it could get to Bauer’s point about being “open for business” in the eyes of the law.

It’s also worth remembering that the initial email about the meeting from music promoter Rob Goldstone indicated that the offer was “part of Russia and its government’s support for Mr. Trump.” Was this an understood fact within the campaign?

Did Trump encourage Stone to build a relationship with WikiLeaks? The indictment of Roger Stone includes a tantalizing comment about his having been asked to contact WikiLeaks by a “senior campaign official” who had been instructed to reach out to Stone. Who was that official? Was it Trump?

Does Stone’s involvement with WikiLeaks go any further than what we already know? It doesn’t appear as though Stone had any direct contact with WikiLeaks beyond late-campaign Twitter messages mostly focused on WikiLeaks telling him to stop claiming a relationship with it.

Was that it? Did he, as his colleague Jerome Corsi has insisted, try to get WikiLeaks to release material related to Clinton campaign chairman John Podesta in the wake of The Washington Post’s publication of the “Access Hollywood” tape?

How does the end of the investigation affect a Stone associate’s fight over a subpoena? What, if anything, did he know? One of several separate legal fights that have been underway has involved a Stone associate named Andrew Miller. Miller, who worked for Stone on and off for years, refused a subpoena from Mueller’s team, leading to his being held in contempt of court.

Miller may be picking the fight to raise constitutional questions about Mueller’s role — or he may be using that argument to protect the information Mueller seeks. How important his information might be is unclear.

Did Trump have more significant conversations about the Moscow deal than we know about? Former Trump attorney Michael Cohen admitted that he lied to Congress about the duration of talks centered on a possible construction project in Moscow. Those conversations — which involved, at one point, Cohen speaking with an aide to Russia President Vladimir Putin’s spokesman — ended in June 2016, shortly after the meeting at Trump Tower.

Trump’s legal team alleges that Trump’s involvement was minimal and that the project itself was mostly abstract.

Did Russia actually do sophisticated targeting of American voters? We know, because of public indictments from Mueller, how Russia allegedly tried to affect the 2016 campaign. First, it allegedly organized an effort on social media to exacerbate political tensions and to bolster Trump’s candidacy. Second, it allegedly hacked the DNC and Podesta and transferred the bulk of that stolen data to WikiLeaks.

The latter had a clear effect on the campaign. The former, a detailed analysis of the targeting allegedly undertaken by Russian accounts reveals, didn’t. Did Russia do something else that depended on or leveraged information from the Trump campaign?

Which company engaged in a separate legal fight over a subpoena? How does it fit in? Another of the ancillary legal fights surrounding the Mueller inquiry involves a foreign company that has been trying to avoid responding to a subpoena from Mueller. How it fits into the broader investigation isn’t clear.

What campaign staff members were told about George Papadopoulos’s and Carter Page’s interactions with Russia? In March 2016, as he battled for the Republican presidential nomination, Trump introduced a slate of foreign policy advisers meant to demonstrate the robustness of his campaign in that arena. Two of those advisers, Papadopoulos and Page, soon came under investigation by federal authorities for their links to Russia.

Papadopoulos was told in April 2016 — shortly after the DNC network and Podesta’s email had been accessed — that the Russians had a cache of incriminating emails for use against Clinton. The next day, he emailed a Trump campaign official to say that he had “some interesting messages coming in from Moscow about a trip when the time is right.” The comment about a “trip” probably refers to Papadopoulos’s efforts to get Trump to travel to Russia — but it’s not clear what else he might have shared about what he learned.

Page traveled to Moscow in July 2016 with the campaign’s permission. After speaking at an event, he emailed the campaign to say that he’d had a conversation with then-Deputy Prime Minister Arkady Dvorkovich. Dvorkovich, Page wrote, had “expressed strong support for Mr. Trump and a desire to work together toward devising better solutions in response to the vast range of current international problems.”

How did Trump Jr. end up at an NRA event with Alexander Torshin? In May 2016, two people contacted the campaign to connect it with a Russian official named Alexander Torshin. Torshin was a longtime member of the National Rifle Association who worked with Maria Butina. Butina last year admitted to conspiring to act as a foreign agent of Russia.

One of the emails to the campaign had the subject line, “Russian backdoor overture and dinner invite.” The campaign reportedly rejected the outreach, but, later that month, Torshin ended up meeting Trump Jr. at an NRA event in Kentucky.

What sealed indictments might exist? A broader question about the Mueller investigation is whether sealed indictments exist that haven’t been made public or resulted in arrests. As Wired’s Garrett Graff presents it, there is an “abnormally large number of sealed indictments filed over the last year in DC federal court, the jurisdiction where Mueller has been worked, including 14 added between August and November — a period where Mueller was theoretically 'quiet’ around the midterm election — and four recent sealed indictments that seemed to parallel the Stone indictment.”

It’s unclear whether there are any sealed indictments related to the Mueller inquiry.

Was Trump honest in his responses to Mueller’s written questions? Shortly after last year’s midterm election, Trump offered written responses to questions posed by Mueller’s team. The content of those questions and answers is broadly unknown — as is the extent to which Mueller’s investigators might have found conflicts in what Trump wrote.

What did the Justice Department prevent Mueller from exploring? One qualification included in the regulations covering Mueller’s work was that the Justice Department had veto authority over what Mueller wanted to investigate or significant actions he sought to take. In other words, if Mueller wanted to indict Person X, he had to clear it with the department.

Once Mueller’s inquiry is done, Barr will have to reveal to Congress those investigations or indictments that his department declined to let Mueller pursue. This could provide insight into why some questions remain unanswered — and could provide a road map for congressional investigators.

What don’t we know that we don’t know? What’s above, using former defense secretary Donald H. Rumsfeld’s famous formulation, are the known unknowns, the things we know we don’t know. But there are also almost certainly unknown unknowns.

Think back to October 2017, when Mueller dropped the first indictment against Manafort and Gates. At the same time, the special counsel’s office released a plea agreement with Papadopoulos, who, at that point, was famous mostly for being added to Trump’s foreign policy team despite having no apparent experience. Then, suddenly, we learned that he’d had repeated contacts with Russians — contacts that, we learned later still, ended up triggering the entire counterintelligence inquiry of the campaign in July 2016.

In other words, Mueller’s team kept him under wraps for months, with barely a hint of his importance. It’s a reminder that we may have no idea what Mueller may still reveal.