Write it off as “performance art” if you wish, but in many decades of watching politics I’ve certainly never heard anything quite like Donald Trump’s attacks on Ben Carson yesterday in a CNN interview and an Iowa appearance. AP’s Jill Colvin has the basics:

Republican presidential candidate Donald Trump, brushing aside any recent claims of civility, has equated Ben Carson’s childhood “pathological temper” to the illness of a child molester, questioned his religious awakening and berated voters who support him.

“How stupid are the people of Iowa?” declared Trump during a rally at Iowa Central Community College. “How stupid are the people of the country to believe this crap?” For more than an hour and a half Thursday night, the billionaire real estate mogul harshly criticized not only Carson, but many of his other competitors in the race for the GOP presidential nomination….

Trump previewed his attack line in an interview with CNN Thursday in which the businessman pointed to Carson’s own descriptions of his “pathological temper” as a young man.

“That’s a big problem because you don’t cure that,” Trump said. “That’s like, you know, I could say, they say you don’t cure — as an example, child molester. You don’t cure these people. You don’t cure the child molester.” Trump also said that “pathological is a very serious disease.”

In his book “Gifted Hands,” Carson described the uncontrollable anger he felt at times while growing up in inner-city Detroit. He wrote that on one occasion he nearly punched his mother and on another he attempted to stab a friend with a knife.

Trump went on to conduct a pantomine of the knife-stabbing incident to show the unlikelihood of ‘Carson’s account, but let’s don’t let him distract us from the unbelievable audacity of comparing a fellow presidential candidate with a child molester.

Most of you have probably heard the ancient and probably apocryphal story of Lyndon Johnson instructing his campaign manager during an early congressional race to spread a rumor that his opponent, a farmer, was in the habit of enjoying carnal relations with his barnyard sows. “Hell, Lyndon,” the campaign manager replied. “You can’t call him a pig-f*****!” Nobody’s going to believe that.” “Yeah,” LBJ supposedly replied. “But I want to hear the SOB deny it.”

Trump’s slur could be worse than that, especially given the crucial distinction that it wasn’t conveyed in a whispering campaign but right out there in public by the candidate himself.

Has Trump finally gone too far? That’s hard to say; if so, the “child molester” line could benefit Carson not only by stimulating sympathy for him but also distracting attention from another emerging story about Carson’s longtime close friendship and business partnership with a dude who pled guilty to felony charges of health insurance fraud.

Regular readers know I have no use for Ben Carson, and I’ve certainly accused him of saying and apparently believing crazy things. But this is beyond any conceivable limits.

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Ed Kilgore is a political columnist for New York and managing editor at the Democratic Strategist website. He was a contributing writer at the Washington Monthly from January 2012 until November 2015, and was the principal contributor to the Political Animal blog.