When Donald Trump ran for president, many voters admitted to concerns about his lack of knowledge and experience, but justified their vote in his favor by saying that his decisions would be enhanced, or if necessary restrained, by the more seasoned people he would gather around him. The president doesn't run everything all by himself, after all, and if President Trump had an impulse to do something rash, presumably his staff would be able to talk some sense into him.

With this presidency only six months old and existing in a state somewhere between crisis and chaos, it's a good time to ask whether Trump can in fact be pulled back from the ledge by his advisers. Because pretty soon we might have the chance to find out, with the stakes enormously high.

Before we get to the Russia investigation and the potential for a constitutional crisis, consider this report in The New York Times about Trump's recent decision to certify that Iran is complying with the terms of the nuclear deal negotiated by the Obama administration, which the president is required to do every 90 days:

At an hourlong meeting last Wednesday, all of the president's major security advisers recommended he preserve the Iran deal for now. Among those who spoke out were Secretary of State Rex W. Tillerson; Defense Secretary Jim Mattis; Lt. Gen. H. R. McMaster, the national security adviser; and Gen. Joseph F. Dunford Jr., the chairman of the Joint Chiefs of Staff, according to an official who described internal discussions on the condition of anonymity. The official said Mr. Trump had spent 55 minutes of the meeting telling them he did not want to. [The New York Times]

As a candidate, Trump had promised to tear up the deal (as did many of his primary opponents), and claimed that with his unparalleled dealmaking prowess he'd be able to negotiate a new one. No one who knew anything took that seriously — the existing deal took years to negotiate, and if the deal collapsed, Iran would be free to pursue nuclear weapons, which would be exceedingly problematic. His national security advisers understand that, and presented Trump with a united front to persuade him not to indulge his infantile urge to do the opposite of what Barack Obama did in every situation. But it obviously wasn't easy.

Mattis and McMaster in particular may be the most sober and experienced people Trump has appointed. But let's consider what will happen when a similar discussion takes place regarding Trump's reaction to the Russia investigation. Who is going to convince him of the wisdom of prudence and caution? Reince Priebus, for whom he clearly has little respect? Stephen Bannon, who wants above all to stay in Trump's good graces so he can keep pursuing his nationalist vision? Jared Kushner, who may want the investigation to go away as much as Trump himself does? Newly appointed communications director Anthony Scaramucci, who seems more like a smooth-talking cable news talking head than an actual adviser?

Special Counsel Robert Mueller was appointed only two months ago, so his investigation has barely begun; by way of comparison, the Whitewater investigation of Bill and Hillary Clinton lasted nearly seven years. Yet there is already a Category 4 freakout in the Oval Office. There seems to be a new "shakeup" of Trump's legal team every few days. Trump went on a public tirade against Attorney General Jeff Sessions, saying he would never have appointed him if he knew Sessions would recuse himself from the Russia investigation (which Sessions was legally obligated to do). And now, according to The Washington Post, Trump is livid about Mueller's investigation. "He has told aides he was especially disturbed after learning Mueller would be able to access several years of his tax returns." Most disturbingly, "Trump has asked his advisers about his power to pardon aides, family members, and even himself in connection with the probe."

The longer the investigation goes on and the more it delves into Trump's business practices, the angrier — and more legally exposed — Trump is likely to get. While nothing has been proven, let's just say that the chance that no laws were broken in Trump's various dealings with a panoply of shady characters over the years is rather small. Yet Trump plainly believes that the rules don't apply to him. After all, that's the way it has always been before. He paid a fine here, negotiated a deal there, and he got away with everything, not to mention the fact that he won an election in which everyone told him that what he was doing was crazy and he couldn't win. The outcome only validated Trump's belief that rules and norms are for losers.

So it isn't hard to imagine that after some new revelation, Trump will call in senior members of his staff and say, "That's it! I'm shutting this thing down. I want Mueller fired." Will any of those in the room speak up and say, "Mr. President, that would be a disaster"? And if they do, will he listen to them? After all, this isn't just about some foreign country — it's personal.

If he does issue the order to fire Mueller, the task would fall to Deputy Attorney General Rod Rosenstein, who appointed Mueller in the first place. There's a strong chance it could trigger another Saturday Night Massacre, the occasion during the Watergate scandal when President Nixon ordered Attorney General Elliot Richardson to fire Archibald Cox, who was investigating the matter. Richardson refused and resigned; then Deputy Attorney General William Ruckelshaus also refused Nixon's order to fire Cox and resigned; it finally fell to Solicitor General Robert Bork, who fired Cox.

We don't know what Rosenstein would do, but there is a strong chance that given the remarkable historical parallels and his reputation as an upstanding public servant, Rosenstein would refuse. In any case, an order to fire Mueller could trigger a constitutional crisis, as the president would be attempting to shut down an investigation into his own misdeeds and those of his family and advisers. You might even see Republicans in Congress objecting.

The same could happen if Trump starts waving pardons around, particularly when they would be intended so obviously to protect himself and his family. Those advising Trump might tell him it's a bad idea politically, but how many would quit in protest? If Trump genuinely saw the specter of his own demise before him from an investigation he believes is inherently illegitimate, they might not be able to talk him out of it even if they tried.

So in the end, whether we face a genuine constitutional crisis comes down to President Trump's ability to think rationally and act with restraint. That doesn't offer a lot of reason to be reassured.