Now the Good Joe/Bad Joe pendulum takes a swing back to the dark side. As in pitch-black, can’t-see-anything-but-evil-journalism dark.

The author of “The Rogue: Searching for the Real Sarah Palin” has sustained his share of bruises for unsubstantiated gossipmongering, most expertly from two reviewers in the New York Times. Now I want a turn.

The astonishing point about McGinniss’s Palin smears is not just that they almost uniformly rest on, like, one anonymous source; or that they cover everything from drugs to sex to bad parenting to laziness to infidelity to shutting yourself in your bedroom the moment you get home; or that they are expressed with a glib certainty not supported by the accompanying documentation — or lack thereof.

The astonishing point about McGinniss’s Palin smears is that he manages to stack two, unrelated ones onto a single page of text. It’s a compact and shameful moment in the history of political biography.

On page 146, McGinniss takes a quote from “a friend” — presumably of Sarah Palin’s — and just prints it as fact:

“It was me, Todd, Sarah, five or six other people, and Todd and Sarah had a fight, so Sarah was riding [on a snowmobile] with somebody else. The cocaine was free flowing. Somebody found a fifty-five-gallon oil drum and turned it upside down and we were all doing cocaine lines off the top of the drum.”

Who knows just what sort of associative storms were swirling in McGinniss’s head at that moment, but somehow he thought the cocaine allegations would be elided into this graph:

Neither did Sarah find nourishment in the joy of sexual intimacy with her husband. “Todd complained a lot about never having sex with Sarah,” a friend of his tells me. “He’d say, ‘I must have gotten laid at least four times, ‘cause I got four kids.’ ”

Just to keep count here — in the course of just a few graphs, we have a nonsense allegation of drug use, a nonsense and irrelevant allegation of sex withholdance, and an element of misogyny as well, in the form of a standard and chauvinistic complaint of the put-upon married man whose wife has borne him several children yet doesn’t put out quite the way he’d like.

Hold on here, readers: Let me go to the acknowledgements of “The Rogue” and see if McGinniss’s editor and literary consigliere is a guy. What do you know? In the first graph of his thank-yous, McGinniss credits guy Dennis Holahan “for so many things,” including “friendship, guidance, and unflagging support.” The rest of the acknowledgements cites five men and a single woman, not including McGinniss’s wife, Nancy Doherty.

So perhaps that gender balance in the acknowledgments explains why McGinniss gets away with blaming the mother of four for not properly pleasing her husband in the sack.

That’s not to say that McGinniss isn’t even-handed in his exploration of civically irrelevant journalism about the sex life of the Palin family.

Just around the corner from the Massacre of Page 146, McGinniss is at it again, this time in reference to Todd Palin. When the First Dude takes off for his “annual escape” to his native Dillingham, writes McGinniss on page 169, juicy things happen — at least according to another “friend.”

“Todd’s a player, especially when he’s out there at fishing camp. I could probably fill up most of my fingers with the names of women Todd has screwed in Dillingham. That man has sowed his oats.”

The quotee goes on to note that those women are “still caught up in drugs,” thereby satisfying McGinniss’s requirement that reporting on drugs and sex be commingled.

Fortunate thing that McGinniss is writing a book, because not a word of this material would take flight in any decent newsroom in the country. Best as we can tell, McGinniss justifies these intrusions on the rationale that Palin is the ultimate public figure, and a disreputable one at that. The public record is full of nasty and vindictive and stupid things she’s done. Therefore, why not throw into print absolutely everything that can be harvested?

Well, precisely because she has a record of pettiness. In scorching the bush of Alaskan politics, Palin has kicked up a lot of detractors. Those detractors are inclined to tell exaggerated tales about the exploits of their ex-governor. So racy anecdotes about Palin’s past require more than your daily recommended dosage of supporting sources and documentation, not less, as is the McGinniss standard.