A friend of President Donald Trump says that Trump is “considering perhaps terminating” special counsel Robert Mueller — an action that, if carried out, would mean a crisis over the rule of law in the United States.

The friend — Christopher Ruddy, founder of the conservative website Newsmax — told Judy Woodruff of PBS NewsHour that the president is considering firing Mueller, who is overseeing the Russia investigation. “I personally think it would be a very significant mistake,” Ruddy said. Here’s the video:

Chris Ruddy to @JudyWoodruff: President Trump is considering firing special counsel Robert Mueller, who he considered for another position. pic.twitter.com/X4IIHlh8at — PBS NewsHour (@NewsHour) June 12, 2017

Ruddy is a longtime friend of Trump and has reportedly been in touch with the president and his close aides at various points this year.

On Monday night, White House press secretary Sean Spicer emailed reporters with a statement that conspicuously did not deny Ruddy’s claim, but merely claimed that he didn’t hear it from Trump directly. “Mr. Ruddy never spoke to the President regarding this issue. With respect to this subject, only the President or his attorneys are authorized to comment,” Spicer wrote.

Politico’s Josh Dawsey confirms that Trump has indeed discussed this possibility with associates, but a source tells him that Trump isn’t currently “likely” to go through with it.

Source says Trump is currently not "likely" to do this but that it remains an option he has discussed with associates. https://t.co/XmfncLf9Lm — Josh Dawsey (@jdawsey1) June 12, 2017

As Matt Yglesias wrote Monday, various Trump allies in the conservative media have recently started to urge the president to fire Mueller. The pretexts they offer differ — some say Mueller is too close to that untrustworthy leaker James Comey, some profess to believe there’s no need for an investigation into Russian interference at all, and others complain that Mueller is hiring some attorneys who have donated to Democrats in the past.

But no matter the pretext, the firing of Mueller — who was appointed by Trump’s own hand-picked deputy attorney general, Rod Rosenstein, less than a month ago — would have seismic implications. It would essentially be a declaration by President Trump that he is willing to fire anyone who dares to investigate him or people close to him. And it would make very clear that he is terrified about just what Mueller might have uncovered.

It would also mean Republicans in Congress would have to face a choice: Are they willing to defy the president and pass legislation to ensure that the Russia scandal is investigated and the rule of law is protected in America?

Or will they choose to become knowing participants in what would then unmistakably be a presidential cover-up?

The firing of Mueller would be reminiscent of Richard Nixon’s Saturday Night Massacre

If Trump fires Mueller, it would hardly be unprecedented. In fact, it’s just what Richard Nixon infamously did on October 20, 1973, in what became known as the “Saturday Night Massacre” — when he ordered the special prosecutor investigating the Watergate break-ins fired, and the attorney general and deputy attorney general resigned in protest rather than go through with it.

“The term ‘Constitutional crisis’ has been overused in the course of the year. … But now this may be the real thing,” journalist Elizabeth Drew wrote at the time in what became her book Washington Journal. Here’s what happened:

President Nixon ordered Attorney General Elliot Richardson to fire special prosecutor Archibald Cox. Richardson refused, and resigned rather than carry out the president’s order.

Then Deputy Attorney General William Ruckelshaus was in charge of the Justice Department, so Nixon ordered him to fire Cox. Ruckelshaus also refused to do so, and resigned.

Now Solicitor General Robert Bork was in charge. He agreed to carry out Nixon’s instruction to fire Cox, and abolished the office of the special prosecutor.

Over the next 11 days, a tremendous public uproar ensued, and criticism from Republicans poured in. On November 1, then, the administration announced they’d appoint a new special prosecutor, Leon Jaworski. Furthermore, Bork said that the president had agreed not to fire Jaworski unless he’d have bipartisan support among congressional leaders.

Jaworski ended up keeping his job, and his investigation moved forward. What he (and Congressional investigators) found over the next nine months led to Nixon’s political collapse and resignation to avert certain impeachment.

So in the end, Nixon’s effort to kill the investigation by firing Cox didn’t work. But keep in mind that that outcome wasn’t guaranteed at the time. In fact, Drew chronicles the feeling of uncertainty and even terror that many felt during those 11 days between Cox’s firing and Jaworski’s appointment — particularly when Nixon declared a worldwide military alert for vaguely explained reasons.

What would it take to fire Mueller?

One somewhat important question here is whether Trump can fire Mueller simply on his own authority, or whether he’d have to go through Attorney General Jeff Sessions (who has recused himself) and Deputy Attorney General Rod Rosenstein (who appointed Mueller and seems unlikely to want to fire him) in order to do so. That would mean firing anyone who fails to comply, as Nixon did.

Mueller’s appointment as special counsel comes under regulations written back in 1999, during Bill Clinton’s presidency. Neal Katyal, who headed the Justice Department’s internal working group drafting the regulations back then, recently wrote in the Washington Post about his interpretation of them. Importantly, he argues that Trump would have to go through Rosenstein to fire Mueller (or to fire Rosenstein and get someone else to do it). Alternatively, he’d have to order the special counsel regulation repealed:

The regulations provide that Mueller can “be disciplined or removed from office only by the personal action of the Attorney General” (again, Rosenstein here, because Sessions is recused) and only for “good cause.” The president, therefore, would have to direct Rosenstein to fire Mueller — or, somewhat more extravagantly, Trump could order the special-counsel regulations repealed and then fire Mueller himself.

It’s worth noting that before the Saturday Night Massacre, there was some question over whether Nixon could fire Cox directly. And Cox decided to preemptively give his own answer to that question. Earlier on that famous Saturday in October 1973, he held a press conference.

Recounting what happened, Drew wrote in Washington Journal, “He [Cox] says he does not believe that the President can fire him; only the Attorney General can. Otherwise, he will go to court and challenge the President.” So in the end, Nixon decided to go through the Justice Department to make sure he was on firm legal ground.

In the end, however, if Trump wants badly enough to fire Mueller, he will manage to do so. And if he does, it will be up to Congress to try to ensure there is a thorough investigation — either through their own inquiries or perhaps by reinstating the old independent counsel law, which created a special prosecutor who couldn’t be fired by the president.

Or they could choose to do nothing at all.