THIS WEEK, The Washington Post ran, for the first time, a comics-page strip in which a character declared former Nixon attorney general John Mitchell guilty for Watergate crimes.

All it took was 41 years, the cartoonist’s hiatus and a “Flashback” comic that was not technically a rerun in The Post because, well, it never ran the first time.

You mean The Post — the paper that won a public-service Pulitzer for its Watergate-affair coverage, led by the legendary reporting of Bob Woodward and Carl Bernstein — refused to run a political cartoon about the case against Nixon’s 1972 campaign director? And in an era when Herblock was drawing cartoons that traced Watergate directly to the White House?

Well, in a phrase: Guilty, guilty, guilty.

On Monday, to kick off a weeklong Watergate-themed story arc, The Post’s Style section ran a famed 1973 “Doonesbury” strip in which radio host Mark Slackmeyer — in rendering a political “obituary” — lets out a punch line that hits quick like a Tommy gun, as Mitchell the Watergate-era defendant is judged by the DJ to be “Guilty! Guilty, guilty, guilty!!”

(Mitchell — who famously once issued a colorful body-part warning to then-Post publisher Katharine Graham over the paper’s Watergate coverage — would, of course, be found guilty in 1977.)

The comic resurfaces because while “Doonesbury” creator Garry Trudeau is on open-ended hiatus from his daily strip (he’s still providing fresh Sundays), The Post is publishing his reruns, and the current offerings — as selected by Trudeau and his syndicate, Universal Uclick — are from 1973.

Trudeau’s syndicate tells Comic Riffs that it had never before offered the “Guilty, guilty, guilty!!” strip as a vacation/sabbatical/hiatus replacement — meaning readers had never before seen it on The Post’s comics pages.

Which raises a question that rings as relevant as ever when it comes to why newspaper editors spike certain strips: Why, exactly, did The Post kill the John Mitchell cartoon the first time, in May of 1973?

After all, The Post was publishing the work of staff cartoonist Herblock, who was wielding those very trade tools of caricature, hyperbole and visual satire to go after the Nixon administration.

From 1972 to 1974, in fact, Herblock targeted similar game frequently. “I have reviewed all of Herb’s cartoons from June 17, 1972 to Aug. 9, 1974 — from the Watergate break-in to Nixon’s resignation. There are 140 relating to Watergate!” Woodward tells The Post’s Comic Riffs this week. (Woodward, now a Post associate editor, will illuminate Herblock’s Watergate work during his Herblock Prize Lecture, titled “The Genius of Herblock: Understanding the Real Nixon,” on Tuesday evening at the Library of Congress.)

By 1973, too, the newspaper industry was well-aware of how “Doonesbury” — launched three years earlier — worked, and how the young Trudeau, a Yale campus cartoonist at the start of the decade, was redefining what mainstream comic strips could do, even in the wake of satire as practiced by Walt Kelly and Al Capp.

” ‘Doonesbury’s’ well-earned popularity is based on the pithy way in which its characters sink their teeth into contemporary subjects. The strip is created with a sure-handed sophistication that is pointed even when it isn’t funny,” Robert C. Maynard — a man who knew a little something about pioneering journalism — wrote in a Post editorial shortly after the John Mitchell strip was pulled.

The plot twist was, The Post’s spiking of “Doonesbury” did not pass unnoticed.

On the contrary, “It was a very big deal for me at the time,” Trudeau tells Comic Riffs this week. “I’d never been booted from so many papers at once, and the Post was such a surprise.”

So what was The Post’s rationale? In his editorial at the time titled “A Comic Strip Isn’t a Court,” Maynard quoted Post managing editor Howard Simons’s explanation: “If anyone is going to find any defendant guilty, it’s going to be the due process of justice, not a comic strip artist. We cannot have one standard for the news pages and another for the comics.” (That last sentence, we’ll let just sink in for a moment.)

Maynard concluded in his editorial that there is a line “across which responsible expression cannot step without running the risk of excision. Trudeau, in my opinion, stepped across that line in having Mark speak as he did.”

“Doonesbury” was carried in about 300 newspapers at the time, and more than a dozen pulled the Mitchell strip, including the Boston Globe, the Baltimore Sun and the Los Angeles Times. Maynard quoted Globe editor Tom Winship as saying: “It’s a beautiful strip, but I have no trouble with this decision.” And a Times executive was quoted in news stories as saying his paper did not run the strip because it “in effect convicts John Mitchell.”

So what was the up-shot of the thumbs-down? Well, the reaction was manifold.

First hummed the phone lines. The Post got at least “500 telephone calls from disappointed readers, wanting to know what had become of ‘Doonesbury,’ ” Maynard reported. (The Globe and the Sun also received enough complaints that editors said “Doonesbury” news items would be warranted.)

Then came the letters. Wrote Bonnie Westley of Gaithersburg, in part, in reaction to The Post’s Maynard editorial: “It amazes me that an intelligent and sophisticated man can come up with such a flimsy excuse for censorship.” And Alice Omohundro of Washington wrote: “As has been pointed out, a newspaper is not bound by the same procedures as a court of law. Therefore, it seems to me that the Post was totally unjustified in refusing to extend to Doonesbury the same rights it claims for itself.”

And Trudeau’s reaction at the time? He told the New York Times: “My highest priority is entertainment. I wasn’t saying John Mitchell was guilty. It was a parody on all the people who are over-reacting.” (In other words: Some editors may have wrongly interpreted Slackmeyer the character as being a pure and literal mouthpiece for Trudeau’s own feelings.)

Two years later, Trudeau would win the Pulitzer Prize for his Watergate commentary — including his “stonewalling White House” strips — making “Doonesbury” (its profile raised by each news article about such controversies) the first comic strip ever to win the editorial cartooning prize. And two years after that, Mitchell — found to be guilty — would begin serving a 19-month prison sentence. (Mitchell died in 1988, and was buried at Arlington National Cemetery.)

Over more than four decades, of course, “Doonesbury’s” satire has tested the sensibilities and journalistic beliefs and boundaries of newspaper editors, often resulting in spiked strips. But for Trudeau, it was the “Guilty, guilty, guilty!!” strip that sparked that first big journalistic jolt.

Letters to the Editor published in The Washington Post, June 1973: