As I sat a few feet from President Trump while he ripped special counsel Robert Mueller and warned Democrats he is preparing a devastating counterpunch, the phrase “The Gathering Storm” came to mind. That’s the title of Volume I of Winston Churchill’s masterful history of World War II.

It also describes the president’s mood and the vicious game of blood sport playing out in Washington. While our nation’s political battles are hardly as dramatic as the fight with Nazi Germany and Japan, a storm is gathering in America and 2019 is shaping up as an extremely turbulent year.

Trump is under siege and girding for a political, legal and public-relations war. Though the conflict began the day he took office, the last two years have been skirmishes compared to the climactic battles ahead.

That view was strengthened by the Oval Office interview last week where I, along with Post reporters Nikki Schwab and Marisa Schultz, spent nearly 40 minutes with the president and several aides.

Trump, sitting behind the grand Resolute Desk, made from the timbers of a 19th century British sailing ship, was genial and gracious. No questions were taboo, and he was in a sunny mood.

Yet his answers exposed a furious frustration over the Mueller probe and Dem plans to use control of the House to swamp his administration with subpoenas and investigations.

“Mueller would like it to go for the rest of his life,” Trump said when asked how he saw the probe ending. “It’s a witch hunt at the highest level, it’s McCarthyism.”

After he mentioned Paul Manafort, I asked whether a pardon for his former campaign manager was possible. “It was never discussed, but I wouldn’t take it off the table,” Trump said. “Why would I take it off the table?”

That answer quickly ricocheted around Washington and sharpened the battle lines, with Dems accusing the president of sending a signal to Manafort that he would be protected in exchange for loyalty.

Some 24 hours later, the drums of war were beating even louder as Michael Cohen pleaded guilty to ­lying to Congress about a possible Trump building project in Moscow.

The president, in public comments, offered a two-part response, saying Cohen was “weak” and looking to get reduced jail time. He also said that, even if the negotiations ran longer in 2016 than Cohen initially laimed, it didn’t matter because Trump was still a private citizen legally running his business.

Like everything else involving Mueller, the Cohen plea offers lots of smoke, but no sign of fire. It might be a piece of a larger puzzle, but more than two years after the FBI probe began, a clear picture ­remains maddeningly elusive.

And yet the probe, and the left’s exploitation of it, continue to inflict casualties. The most recent one is that any hopes that divided government might be productive are vanishing.

The day after the midterms, Trump tried to paint a rosy picture of the Dem majority in the House, saying he was eager to work with likely Speaker Nancy Pelosi and would sign key legislation even if most Republicans opposed it.

Now his message is far more stick than carrot. As he said in our interview, the new Dem leaders would be unleashing the furies from hell if they engage in “presidential harassment.”

“I will hit them so hard, they’ve never seen a hit like that,” he said, referring to his power to release secret documents, some of which, he hinted, will be deeply embarrassing to Barack Obama’s administration.

“If they want to play tough, I will do it,” he said. “And they will see how devastating those pages are.”

I believe the president should release any such documents now, regardless of their partisan impact. Excessive secrecy serves only to hide official wrongdoing and the lack of transparency fuels public mistrust.

In theory, Trump agrees. But he is fixated on the war, and understandably so because he is fighting for the survival of his presidency.

His theory on the origins of the war is familiar — and credible: The allegations of Russian collusion were a tissue of lies supported only by the discredited dossier secretly financed by Hillary Clinton. Those lies were given a sheen of credibility by a corrupted FBI investigation that lives on through Mueller.

“I’m sure [fired FBI Director James] Comey had someone above because you know there’s no question that [then CIA-boss] John Brennan was involved,” Trump said. “There’s no question that all of these people you see on television, all of these lightweights were involved, and it’s hard to believe that the president wasn’t involved.

“And the only reason they were doing it was just in case I won.”

As for the dossier, Trump asks: “So why isn’t Mueller looking at that? Russians were paid for the phony dossier. Now it’s been discredited, it’s total baloney, but a lot of money was passed.”

We had stayed long past our allotted time, and as we left, aides handed us six pages listing the ­administration’s accomplishments. They include the historic low unemployment among Latinos and black Americans, rising wages and the fact that 4.4 million people no longer need food stamps.

Consumer and business confidence are soaring and America is now the world’s largest producer of oil and natural gas. Kim Jong-un is sending flattering letters to Trump instead of firing off missiles, and a new trade agreement with Mexico and Canada keeps faith with the vow to fix NAFTA.

Those are some of the highlights of a remarkable two years, but on most days, they are eclipsed by the political war. And the worst is yet to come.

Triumph of faith

After a teacher in New Jersey told first-graders there is no Santa Claus, elves, Easter Bunny or magic of any kind, the kids were heartbroken and their parents furious.

Fortunately, there is a timeless cure for unbelief.

An 1897 editorial in the New York Sun, written to 8-year-old Virginia O’Hanlon, puts doubt in its place.

“Yes, Virginia, there is a Santa Claus,” writer Francis Church declared.

“Nobody sees Santa Claus, but that is no sign that there is no Santa Claus,” he writes in one magical passage. “The most real things in the world are those that neither children nor man can see.”

Who knows, Church’s ode to faith in all ages might even revive the spirit of the jaded teacher.

An NYC crisis in plain sight

New Yorkers worried about the growing ranks of vagrants, many of them mentally ill, must read Stephen Eide’s op-ed in Friday’s Post . Among the alarming stats and policy dead ends, these sentences stand out:

“The number of ‘emotionally disturbed person’ calls to the NYPD has risen every year since 2014 … Rikers Island is host to a far larger population of seriously mentally ill individuals than any mental hospital in the city or state.”

In other words, your eyes are not lying. The situation really is getting worse.