Call this the year of the wolf. That’s apropos a warning about special prosecutors and their ability to shake presidential confidence. It’s from the pen of one of our most visionary Supreme Court justices, Antonin Scalia.

He’s now gone, alas. You can bet the scales of justice, though, that he would’ve been thinking of President Trump’s boldness as the president and his aides are pursued by Robert Mueller.

What Scalia worried about was the ability of the president to stay focused in a dangerous world. It’s hard to imagine a moment that could have alarmed Scalia more than this one.

It’s not just that the president’s ex-aide Steve Bannon is claiming the campaign’s flirtation with the Russians was “treasonous.” Or boasting that the prosecutor will “crack Don Junior like an egg.”

It’s North Korea threatening to nuke us, Iran sowing war in the Middle East, Russia flexing its muscles, and China maneuvering against us in the South China Sea.

Scalia worried about a prosecutor with an unlimited budget, unmoored from constraints normal prosecutors face, who he feared could affect “the boldness of the president.”

The justice expressed his fears in a case called Morrison v. Olson, in which the court allowed a so-called independent counsel. The “independent” counsel was OK, it reckoned, for he could be fired by the attorney general. That wasn’t enough for Scalia, who wrote one of history’s most famous dissents.

Scalia worried about the impact of a prosecutor pursuing one or several individuals without yet knowing whether a crime had been committed: “Unless it can honestly be said that there are ‘no reasonable grounds to believe’ that further investigation is warranted, further investigation must ensue.”

“The conduct of the investigation, and determination of whether to prosecute,” Scalia continued, “will be given to a person neither selected by nor subject to the control of the president.”

Scalia worried such a prosecutor would assemble a staff from persons “willing to put aside whatever else they are doing, for an indeterminate period of time” to investigate the president.

Sound familiar?

Even if “the boldness of the president himself will not be affected,” Scalia wrote, he worried about the president’s “high-level assistants.”

“Typically,” he pointed out, aides have “no political base of support.” He warned that it would be “utterly unrealistic to think that they will not be intimidated.”

If all this seems like mere constitutional theory, recall what happened in the 1990s. That’s when an independent counsel was sicced on President Bill Clinton.

It came out only later, and in an all-too-horrifying manner, that during this period Osama bin Laden was hatching plans for a war against America. Our intelligence agencies were onto him. At one point, we had surveillance of an al Qaeda lair in Afghanistan. Bin Laden himself may have been within our sights.

On four occasions between 1998 and 2000, Clinton’s national-security adviser, Sandy Berger, was presented with plans to take action. Each time, the administration shrank from doing so, according to the official report of the 9/11 commission, published in 2004.

The commission cited lots of reasons. One of them was that the administration was under “extremely difficult political considerations.”

“Opponents,” it explained, “were seeking the president’s impeachment.”

None of this is to say the president shouldn’t be investigated when there’s cause — indeed, putting the head of government above the law would be itself a threat to democracy. It’s dangerous, though, to have an open-ended, ill-defined investigation that swirls around the White House and follows the president’s aides around like a shadow, impeding their ability to work unnecessarily by a prosecutor’s lack of restraint.

The logic of the moment right now is to protect the boldness of the only president we’ve got.

Scalia stressed the malevolence of an unmoored prosecutor. While issues often come before the court “clad in sheep’s clothing,” he wrote, “this wolf comes as a wolf.”

This is adapted from a column that first appeared in the New York Post.