Since the end of World War II, political writers and presidency scholars have pursued the Holy Grail: fly-on-the-wall access to the White House. It’s an elusive quest never fully realized, although some intrepid scribes have come close. The first was New Yorker magazine writer John Hersey, who gained Harry Truman’s confidence. The most recent is Michael Wolff, an acerbic New York media critic — and Donald Trump’s latest nemesis.

The incentive for presidents to cooperate with such arrangements range from simple vanity to notions of civic duty. For the journalists, the rationale has been the same since Truman’s day. To employ a Cold War phrase that’s back in the news this week, the commander-in-chief has his finger on the nuclear button. Is he tough enough to bear that responsibility? Humane enough? Intelligent enough? Knowledgeable enough? Is the president of the United States a sane and stable person?

After an initial rebuff, John Hersey spent months researching what he called “a conventional profile.” At the end of that time, the writer reiterated his earlier request, telling Truman that with a few weeks’ access to the president, he might produce a genuine contribution to U.S. history. This pitch did the trick, and Hersey subsequently went on morning walks with Truman, attended senior staff meetings — (he was present on the day of China’s incursion into South Korea) — and observed Truman’s speechwriters drafting the 1951 State of the Union message. (These meetings took place in Blair House, as the White House was gutted for a major renovation.)

This arrangement worked for both parties. Hersey got a much richer story. Truman was presented to readers of the New Yorker as a more complex and appealing person than he would have been.

“In these weeks of closer touch with him I was completely captivated by what I saw and heard,” Hersey explained later. “Mr. Truman spoke of himself sometimes in the first person and sometimes in the third — the latter when he was referring to a personage he still seemed to regard, after nearly four years in office, as an astonishing tenant in his own body: the president of the United States. Toward himself, first-personally, he was at times mischievous and disrespectful, but he revered this other man, his tenant, as a noble, history-defined figure. Here was a separation of powers within a single psyche, and a most attractive phenomenon it was, because Mr. Truman moved about in constant wonder and delight at this awesome stranger beneath his skin.”

Readers won’t find such uplifting prose in “Fire and Fury: Inside the Trump White House,” an explosive new book by Michael Wolff. Like the president himself, it’s gossipy and profane, Wolff’s stock in trade. But like Hersey, the author tries to discover the essence of the man with his finger on that big nuclear button. He dispenses his conclusions in passages such as this:

“Trump didn’t read. He didn’t really even skim. If it was print, it might as well not exist. Some believed that for all practical purposes he was no more than semi-literate. Some thought him dyslexic; certainly his comprehension was limited.

“But not only didn’t he read, he didn’t listen. He preferred to be the person talking. And he trusted his own expertise — no matter how paltry or irrelevant — more than anyone else’s. What’s more, he had an extremely short attention span, even when he thought you were worthy of attention.”

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California Republicans: Give a call to your GOP cousins in swing states Americans must decide for themselves whether the difference here is with the chronicled or the chronicler. The most obvious answer is that it’s both. “Donald Trump and Michael Wolff deserve one another,” is how Poynter Institute media writer Jim Warren put it. “They’re like conjoined twins tied at the ego.” Another way of saying this is that the difference between John Hersey and Michael Wolff parallels the difference between Truman and Trump.

Truman was a decorated combat officer in a World War I artillery division. Trump, despite attending military prep school, avoided Vietnam on the basis of four college deferments and a bone spur in one of his heels. Like Truman, John Hersey went to war, as an embedded correspondent in the Pacific. Nearly killed in a plane crash at Guadalcanal, he wrote about the U.S. Marines’ bravery on that island. In 1946, the New Yorker dispatched Hersey to Hiroshima, a place actually targeted by a president deploying the “button.” His reporting, which was later turned into a massive bestseller, forever shaped the conversation about nuclear war. He was a meticulous, courageous, and highly respected journalist, whose closest equivalent today might be Martha Raddatz.

Michael Wolff earned his spurs in less perilous environs: the salons and dinner parties of Manhattan’s Upper East Side. His stock in trade was shrewd, if snarky, insights into powerful media moguls. Wolff gravitated naturally toward Trump, and vice versa, two men not known to be sticklers for the facts.

Trump now contends that he gave no access to Wolff for his book and that its quotes and conclusions are exaggerated or invented. Trump’s assertions cannot be dismissed out-of-hand. Wolff has a reputation for stretching minor encounters in ways that make him sound like he dwells in his subjects’ inner sanctums. There are obvious accuracy problems with the book, beginning with Wolff’s easily disproved contention that Trump never heard of former House Speaker John Boehner.

Trump also lashed out at Stephen K. Bannon, his estranged former campaign adviser and chief White House strategist — and a key Wolff source — who Trump said had “lost his mind.” On Friday, Trump denounced the “author of phony book” on Twitter, adding that he never spoke to Wolff for the project, which he characterized as being “full of lies, misrepresentations and sources that don’t exist.” Then he issued a Trumpian threat: “Look at this guy’s past and watch what happens to him and Sloppy Steve!”

This last reference is to Bannon’s unkempt physical appearance. An ad hominem criticism, in other words. Here, too, Harry Truman provides a telling contrast.

On the last Monday in February 1951, Hersey received a terse message: be at Blair House at 8 p.m. Wednesday. He arrived to find a high-level meeting of Washington’s top Democrats. The agenda was how to respond to the “poison” being spread by anti-communist crusader Joseph McCarthy. Hersey later wrote about what happened. Truman described McCarthy’s habit of spreading toxic innuendo, specifically indiscriminate charges that the State Department was full of communists and homosexuals. It was undermining his administration. What could a president do?

One option concerned a dossier Democrats had compiled, apparently with the assistance of law enforcement, on Joseph McCarthy’s sex life, presumably — though Hersey does not directly say so — with other men. Such activity would have exposed the gay-bashing senator as a self-hating hypocrite. Truman reacted in a flash. Slapping his hand down sharply on the table, he began using his third-person voice. “You must not ask the president of the United States to get down in the gutter with a guttersnipe,” he said.

Now here is a lesson for Trump. Ditto for the FBI, which is apparently still is in the business of peddling dossiers with unverified sexual rumors about politicians. Harry Truman had it right: enough of such talk.

Carl M. Cannon is executive editor and Washington Bureau chief of RealClearPolitics.