The most crucial question in the special counsel’s investigation into the Trump campaign’s ties to Russia has yet to be answered: What about the president himself?

Robert Mueller’s investigation has turned up a lot so far. Thirty-three people have been indicted or pleaded guilty. That number now includes five former advisers to Trump.

And recent news developments suggest that the probe is coming even closer to the president. Already, a leaked draft charging document conspicuously alluded that Roger Stone was in touch with Trump when Stone urged associates to try to get hacked material from WikiLeaks.

Then a new charge against Michael Cohen last week mentioned Trump himself, as well as his business and members of his family. This was in connection with efforts to build a Trump Tower in Moscow during the 2016 campaign. (They were not accused of any wrongdoing.)

Though the special counsel has already charged former Trump advisers with lying about their contacts with Russians, and charged more than two dozen Russians with interfering with the 2016 election through email hacking and social media manipulation, he hasn’t alleged any larger criminal conspiracy between Trump and Russia just yet. But the president recently submitted answers to some questions Mueller sent him, and should he have made false statements, he could face legal consequences.

Mueller has also investigated a plethora of other topics that have not yet been the basis for any charges but could reemerge at any moment: foreign money trails, secret meetings in Seychelles, and the Trump campaign’s digital operation — as well as, of course, the infamous Trump Tower meeting between Donald Trump Jr. and a Russian lawyer.

We could learn more soon. The Mueller investigation “may be coming to its climax, potentially in the next few weeks,” Michael Isikoff of Yahoo News recently reported, citing “multiple sources close to the matter.” At long last, the special counsel may be preparing to show his cards — and reveal what they hold for the future of Trump’s presidency.

What Mueller’s questions for Trump suggest about his suspicions

It’s not entirely clear what line of investigation poses the most danger to Trump himself. But some clues may well lie in those questions Mueller posed to Trump directly — and that Trump finally answered, after 10 months of delay and recalcitrance, shortly before Thanksgiving.

The full set of these questions has not leaked out. However, the Washington Post has reported two key facts: first, that there were about two dozen questions on the final list, and second, that they all focused on events before the 2016 election.

Beyond that, ABC News has reported on at least four topics covered by the questions: Don Jr.’s Trump Tower meeting, Roger Stone and possible WikiLeaks communications, Michael Cohen’s Trump Tower Moscow talks, and a change to the Republican platform regarding Ukraine at the 2016 GOP convention.

That’s all we know about the questions Trump actually answered. However, there was a more expansive earlier version of the question list, assembled by Trump’s legal team based on their conversations with the special counsel from this March, that leaked to the New York Times a while back.

There are five other pre-election topics included on the older list: Trump’s 2013 trip to Russia, his talks about potentially meeting Putin during the campaign, his talks about sanctions on Russia, what he knew about Russian hacking and social media activity during the campaign, and whether he knew of any request for election help from his campaign to Russia.

The questions we do know about have given us a sense of what Mueller is interested in regarding Trump and Russia, albeit an incomplete one.

He appears to have asked about Trump’s relationship with Russia generally, about what Russia could have done for Trump during the campaign, and about what Trump could have done for Russia. Read together, as independent journalist Marcy Wheeler has argued, they seem to show several possibilities for a quid pro quo between Trump and Russia — involving some combination of hacking, social media help, a real estate deal, sanctions, and other policy changes.

So did Mueller just ask about all this to cover his bases? Or has he been amassing evidence and preparing to argue that such a conspiracy did in fact take place — and that Trump himself may have been involved?

Recent Mueller probe documents conspicuously mention Trump

When the special counsel first started filing charges in the probe, the president’s defenders argued — accurately — that those charges didn’t mention anything about Trump himself.

But that’s gotten harder to assert in recent months.

First, there was an oblique reference to Trump in Mueller’s July indictment of Russian intelligence officers on charges of hacking leading Democrats’ emails.

“On or about July 27, 2016, the Conspirators attempted after hours to spearphish for the first time email accounts at a domain hosted by a third-party provider and used by Clinton’s personal office,” the indictment alleges. “At or around the same time, they also targeted seventy-six email addresses at the domain for the Clinton Campaign.”

This detail — and particularly the conspicuous mention that this hacking occurred “after hours” (Moscow time) — confirmed that this hack occurred shortly after Trump infamously said, “Russia, if you’re listening, I hope you’re able to find the 30,000 [Hillary Clinton] emails that are missing.”

Second, there was the draft document outlining a false statements charge against conservative commentator Jerome Corsi, who leaked it last month after Mueller’s team provided it to him as part of plea deal talks.

The document (which we should keep in mind is a draft) asserts that longtime Trump adviser Roger Stone asked Corsi to try to get in touch with WikiLeaks during the summer of 2016, to get ahold of stolen emails the group had.

But it also drops the tidbit that Corsi “understood” Stone to be “in regular contact with senior members of the Trump Campaign, including with then-candidate Donald J. Trump,” around this time. That poses the obvious questions of whether Trump was informed about Stone’s efforts or may have even directed them.

Most recently, in the Cohen plea documents, Trump and unnamed “family members” of his are both mentioned as being briefed on Cohen’s efforts on the Trump Tower Moscow project:

COHEN discussed the status and progress of the Moscow Project with Individual 1 on more than the three occasions COHEN claimed to the Committee, and he briefed family members of Individual 1 within the Company about the project.

Mueller has made no allegation of criminal wrongdoing against Trump or anyone in his family so far. But he sure does seem to be mentioning them more often in documents.

Don’t forget obstruction of justice

It’s also worth a reminder that there’s a separate aspect to the Mueller probe that hasn’t gotten much attention lately: obstruction of justice.

The special counsel was appointed shortly after Trump fired FBI Director James Comey. In the days after the firing, Trump seemed to admit on television that he did it partly because of the Russia investigation. Additionally, news broke that Trump had privately asked for Comey’s “loyalty” and urged him to let the investigation into Michael Flynn go.

So Mueller very quickly began to focus on potential obstruction of justice as an important part of his investigation. His team questioned more than a dozen administration officials, attempting to establish whether Trump was corruptly trying to interfere with investigations into his associates.

The New York Times’s leaked list of Mueller’s proposed questions for Trump, which dates from March, contains many that are about obstruction. Reportedly, none of them made the final list of questions submitted to the president, because Trump’s team insisted they wouldn’t answer questions about his time in office. But the old list suggests Mueller was interested in the following topics:

Trump’s interactions with Comey about the Flynn investigation, and why Trump fired Comey

Trump’s interactions with former Attorney General Jeff Sessions, including efforts to get Sessions to reverse his recusal from oversight of the Russia investigation

Trump’s involvement in Donald Trump Jr.’s misleading public statement about his meeting with a Russian lawyer

Efforts to float pardons to potential witnesses against Trump

Trump’s talks about firing Mueller himself

This week, Trump revived the obstruction of justice issue by tweeting attacks on one cooperating witness — Michael Cohen, who he said was a liar who should serve a complete sentence — and praising another associate, Stone, who has said he’d never testify against Trump. Legal experts debated whether this amounted to witness tampering.

So the new tweets are part of a larger pattern of Trump’s behavior that Mueller has been investigating for well over a year.

What could come next

Finally, even if the special counsel has compiled damaging evidence about Trump, the question remains what he would actually do with that evidence.

It’s widely believed that Mueller won’t actually indict Trump, since the Department of Justice has long held that sitting presidents are immune to criminal indictment.

According to the president’s legal team, Mueller has indicated that he is writing some sort of report on Trump’s conduct. If true, that would resemble the end product of previous investigations into presidents, like independent counsel Ken Starr’s report on President Clinton. And it could kick-start a debate over impeachment in the newly Democratic House of Representatives.

Still, it’s unclear how such a report would be made public — if it is at all. Mueller operates under different legal authority than Starr did, and the regulation under which he was appointed states that the final report on prosecutorial decisions should be confidential. The special counsel has never publicly confirmed that his team is even writing a report.

Marcy Wheeler has put forward the alternative theory that Mueller could instead “speak” about Trump’s conduct through further indictments of other people and other court filings in existing cases.

But until Mueller decides to make his next move, even this — like so much else in his investigation — will remain a mystery to us.