President Donald Trump sharply escalated his attacks on special counsel Robert Mueller over the weekend, making sweeping and controversial claims of presidential power while demeaning Mueller’s investigation as illegitimate.

In a series of tweets and interviews, Trump and his lawyer Rudy Giuliani claimed that Trump’s pardon power is absolute and that he can even use it on himself. Giuliani also argued that Trump couldn’t be indicted as sitting president, even if he shot someone. And Trump asserted that Mueller’s very appointment was unconstitutional.

These new attacks are particularly eyebrow-raising because they come amid a period of relative public quiet on Mueller’s part. The special counsel’s team is known to be looking into a plethora of topics, but they haven’t filed any new charges (that we know of) in more than three months.

One new development is that a pair of letters Trump’s lawyers sent to Mueller’s team — one from this January, one from a year ago — were leaked to the New York Times. The letters make similarly sweeping presidential powers claims, including arguing that the president is empowered to end any investigation he wants, and assert that Trump has no obligation to sit for an interview with Mueller.

All of this comes off as an ominous prelude to some kind of showdown.

But because we have so little insight into what Mueller’s up to, it’s still not clear what exactly such a showdown would be about.

One possibility is that Mueller is preparing a new round of indictments of people close to the president. Another is that he might subpoena Trump if he keeps refusing to agree to an interview. A third is that it’s Trump himself who will provoke the next big crisis, either with a high-profile Justice Department firing or pardons.

We don’t know which of these is the case. All we can tell is that Trump sounds increasingly alarmed about the investigation and is embracing ever more aggressive arguments in response. So here’s how things got more heated in recent days.

The leaked letters revealed Trump’s broad executive power claims, just after he was floating pardons

The background for this weekend’s Trump-Mueller discussions is that on Thursday, Trump pardoned conservative commentator Dinesh D’Souza for campaign finance law violations, and mused about pardoning other celebrity pals of his.

This wasn’t explicitly related to the Russia investigation, but it was widely interpreted as either Trump testing the waters for eventual pardons in the Russia probe or Trump hinting to associates in legal trouble, and those considering “flipping,” that he’ll pardon them eventually. (Last year, Trump’s then-lawyer John Dowd reportedly discussed potential pardons with Michael Flynn and Paul Manafort.)

Then in the middle of the day on Saturday, Trump sent a tweet that supplements his now-standard claims of “no collusion” and the “witch hunt” with a question about whether it was Mueller or the Justice Department leaking his lawyers’ “letters” to the media:

There was No Collusion with Russia (except by the Democrats). When will this very expensive Witch Hunt Hoax ever end? So bad for our Country. Is the Special Counsel/Justice Department leaking my lawyers letters to the Fake News Media? Should be looking at Dems corruption instead? — Donald J. Trump (@realDonaldTrump) June 2, 2018

The New York Times then posted two of those letters.

But before getting into what they say, it’s worth noting that Trump’s legal team, either current or former, seems a more likely source of this leak than Mueller’s seemingly leakproof team. Such a leak could be strategic, but it could also be unauthorized. Keep in mind also that these letters are old (the most recent one was from four months ago) and aren’t necessarily reflective of the newest developments in the investigation.

What are the letters, and what do they say?

The first letter is dated June 23, 2017 — a month after Mueller’s appointment and a little more than a week after reports claimed Mueller was now investigating Trump for obstruction of justice related to FBI Director James Comey’s firing. Written by Trump’s then-personal lawyer Marc Kasowitz, the letter disputes some specifics about what Trump said and did related to Comey and Flynn.

But it also makes a broader claim that “there is no statutory or Constitutional basis” for any obstruction of justice charge against Trump. Kasowitz argued:

That the president “possesses the indisputable authority to direct that any executive branch investigation be open or closed”

That he has the power to remove the FBI director “for any reason”

And that he has “the power to pardon any person before, during, or after an investigation and/or conviction”

The implications for the rule of law are striking. Trump’s legal team has taken the position that Trump is perfectly free to launch investigations into anyone he wants, to end any investigations he dislikes, to fire anyone who won’t carry out his wishes, and to pardon anybody at any time. These claims are all disputed by legal scholars, but they echo Nixon-era arguments that the president is above the law.

The second letter is dated January 29, 2018, and is written by John Dowd (who succeeded Kasowitz as Trump’s personal lawyer before departing earlier this year) and Jay Sekulow (who’s still on the team). This letter is a response to Mueller’s request that President Trump sit for an interview with the special counsel’s team — and basically asserts that he shouldn’t.

Trump’s lawyers write that Mueller’s team’s main questions have already been answered in other forums, and that the White House and campaign have turned over a great deal of evidence. They add that an interview request would “hamper” Trump’s performance of his presidential duties and that “having him testify demeans the Office of the President before the world.”

This second letter also purported to provide answers to several questions Mueller’s team had for Trump (while avoiding others). In one of these answers, Dowd and Sekulow appeared to admit that the president had personally dictated a highly misleading statement that his son Don Jr. released about his Trump Tower meeting with a Russian delegation — something Sekulow had repeatedly denied last year. (The statement claimed the meeting was mainly about adoptions, not mentioning its main purpose was to get Russian-provided dirt on Hillary Clinton.)

The bigger picture takeaway from the letters, though, is that Trump’s lawyers are making sweeping presidential powers claims and asserting vast presidential authority over the Justice Department.

Trump’s tweets then got even more unhinged

Sunday’s news was mainly dominated by a discussion of these letters and Trump’s presidential powers generally, in which Rudy Giuliani, among other things, claimed that Trump couldn’t be indicted even if he shot James Comey in the Oval Office.

Early in the morning, though, Trump mentioned his former campaign chair Paul Manafort in a new pair of tweets:

As only one of two people left who could become President, why wouldn’t the FBI or Department of “Justice” have told me that they were secretly investigating Paul Manafort (on charges that were 10 years old and had been previously dropped) during my campaign? Should have told me! — Donald J. Trump (@realDonaldTrump) June 3, 2018

....Paul Manafort came into the campaign very late and was with us for a short period of time (he represented Ronald Reagan, Bob Dole & many others over the years), but we should have been told that Comey and the boys were doing a number on him, and he wouldn’t have been hired! — Donald J. Trump (@realDonaldTrump) June 3, 2018

The tweets were unusual because Trump hadn’t mentioned Manafort by name on Twitter since the day after his indictment last October. Trump’s team has been hesitant to fully adopt the argument that Manafort — who’s been indicted on 23 bank fraud, tax, money laundering, and other charges — is innocent or was set up somehow. But here Trump seems to allude to that possibility, saying, “Comey and the boys were doing a number on him.”

Finally, on Monday morning, Trump sent an even more remarkable pair of tweets — one asserting that he has the power to pardon himself (but won’t, because he didn’t do anything wrong), and one saying that Mueller’s appointment was unconstitutional (but that he’ll work with it anyway, because he didn’t do anything wrong).

As has been stated by numerous legal scholars, I have the absolute right to PARDON myself, but why would I do that when I have done nothing wrong? In the meantime, the never ending Witch Hunt, led by 13 very Angry and Conflicted Democrats (& others) continues into the mid-terms! — Donald J. Trump (@realDonaldTrump) June 4, 2018

The appointment of the Special Counsel is totally UNCONSTITUTIONAL! Despite that, we play the game because I, unlike the Democrats, have done nothing wrong! — Donald J. Trump (@realDonaldTrump) June 4, 2018

Legal experts are split on whether Trump can pardon himself, and the argument that Mueller’s appointment is unconstitutional is a fringe one, only lately floated by some of Trump’s allies in conservative legal circles.

Trump has been in a cold war with Mueller’s team for much of the year since he was appointed, but these new arguments — suggesting that Manafort may have been set up somehow, bragging that he could pardon himself, and arguing that the entire investigation into him is unconstitutional — all signify a new level of aggression.

What’s unclear is why Trump is escalating now. Is it Trump’s simmering rage about the investigation, or is there some more direct cause behind the scenes?

All this could be Trump trying to make the public case for why he shouldn’t sit for an interview with Mueller’s team — or why he should resist a potential subpoena from them. It could be a panicked response to some development in the investigation Trump is particularly worried about. Or it could be a prelude to some dramatic offensive action on his part.

We don’t know. And one reason we don’t know is that Mueller’s own activity, intentions, and strategy remain opaque. But all of this seems to be headed somewhere very messy indeed.