President Donald Trump pushed Attorney General Jeff Sessions to resign on Wednesday. Matthew Whitaker, Sessions’ chief of staff, who has expressed hostility to Special Counsel Robert Mueller’s inquiry, will step in as acting attorney general and, according to reports, take over supervision of the investigation.

The president has the right to replace his Cabinet officials. After all, it’s not unusual, as Trump said during his news conference earlier Wednesday, to have some turnover after an election.

But the head of the executive branch does not have the right to attempt to end investigations of himself, his campaign and his administration. Those kinds of actions are called abuse of power and obstruction of justice.

For the moment, there’s no sign that Trump is attempting either a rapid or a slow-motion re-enactment of the so-called Saturday Night Massacre of 1973, when Richard Nixon ordered the firing of a special prosecutor, which contributed to the chain of events that ultimately led to the president’s downfall.

Nor do we know how the American people in general or Republicans in Congress in particular would react to such a move by Trump. Several Republican senators have repeatedly warned him not to try; on the other hand, they have refrained from taking pre-emptive actions to make it impossible.

The appropriate action at this point would be for both Trump and the acting attorney general to make clear statements that the investigation will continue without interference.

It would also be appropriate for Judiciary Committee Chairman Chuck Grassley and other Senate Republicans to make public declarations of their respect for the office of the special counsel. They should indicate that they will require any new nominee for attorney general to make the same no-interference pledge that the committee demanded of Elliot Richardson when he was nominated for the job in 1973. It’s promising that Republican Sens. Lamar Alexander and Jeff Flake, and Sen.-elect Mitt Romney all spoke Wednesday about the importance of allowing an investigation to go forward. Sen. Susan Collins of Maine also weighed in.

Whether Senate Republicans fulfill that responsibility or not, Nixon’s example should make it clear to Trump that any actions he takes to subvert the investigation are likely to backfire.

In 1973, Nixon attempted to fire Special Prosecutor Archibald Cox, and eventually found someone to do so after the attorney general and the deputy attorney general resigned in protest. The reaction was so virulent that Nixon was forced within days to back down entirely. A new special prosecutor was appointed and given at least as much independence as Cox had, and Nixon complied with subpoenas that had been the immediate cause of the conflict. Not only that, the Saturday Night Massacre marked the first time in the Watergate scandal that impeachment of the president was not only discussed openly, but thought to be a real possibility.

One can never prove these things, but it’s not a stretch to argue that if Nixon had complied with Cox’s demands in the first place, he might well have survived. Nixon was guilty of the underlying crimes, which were surely impeachable. But Congress might not have acted had it not been for Nixon making it clear the rule of law was on the line.

We cannot know whether public opinion in 2018 would echo what happened in 1973. But we do know that Trump got into this mess in the first place in large part because he fired James Comey, the FBI director, presumably to end the investigation into the 2016 election. That episode appears to have damaged Trump’s approval ratings and certainly damaged his standing in Washington, and brought about Mueller’s appointment as special counsel.

We also don’t know what Mueller’s investigation has found. There’s much speculation about additional indictments and a final report that could harm the president. It is far from clear that trying to force out Mueller would stop any of that. But it will force people to take sides, and Trump should not count on even previously loyal Republicans to follow him into blatant disregard of the rule of law. Many of them didn’t endorse his firing of Comey. They probably wouldn’t support him now, when the incentives for sticking with him are the lowest they’ll ever be. Just as with Nixon, even if Trump might be guilty he could still make his situation a lot worse.

If he cares at all about his presidency, Trump should not go down Nixon’s path.