The charge: The Tucson massacre is a consequence of the “climate of hate” created by Sarah Palin, the Tea Party, Glenn Beck, Obamacare opponents, and sundry other liberal bêtes noires.

The verdict: Rarely in American political discourse has there been a charge so reckless, so scurrilous, and so unsupported by evidence.

As killers go, Jared Loughner is not reticent. Yet among all his writings, postings, videos, and other ravings — and in all the testimony from people who knew him — there is not a single reference to any of these supposed accessories to murder.

Not only is there no evidence that Loughner was impelled to violence by any of those upon whom Paul Krugman, Keith Olbermann, the New York Times, the Tucson sheriff, and other rabid partisans are fixated. There is no evidence that he was responding to anything, political or otherwise, outside of his own head.

A climate of hate? This man lived within his very own private climate. “His thoughts were unrelated to anything in our world,” said the teacher of Loughner’s philosophy class at Pima Community College.

“He was very disconnected from reality,” said classmate Lydian Ali.

“You know how it is when you talk to someone who’s mentally ill and they’re just not there?” said neighbor Jason Johnson. “It was like he was in his own world.”

His ravings, said one high-school classmate, were interspersed with “unnerving, long stupors of silence” during which he would “stare fixedly at his buddies,” reported the Wall Street Journal. His own writings are confused, incoherent, punctuated with private numerology and inscrutable taxonomy. He warned of government brainwashing and thought control through “grammar.” He was obsessed with “conscious dreaming,” a fairly good synonym for hallucinations.

This is not political behavior. These are the signs of a clinical thought disorder — ideas disconnected from one another, incoherent, delusional, detached from reality.

These are all the hallmarks of a paranoid schizophrenic. And a dangerous one. A classmate found him so terrifyingly mentally disturbed that — as she e-mailed friends and family — she expected to see his picture on TV after he had perpetrated a mass murder. This was no idle speculation: In class, “I sit by the door with my purse handy,” she wrote, so that she could get out fast when the shooting began.

Furthermore, the available evidence dates Loughner’s fixation on Rep. Gabrielle Giffords back to at least 2007, when he attended a townhall of hers and felt slighted by her response. In 2007, no one had heard of Sarah Palin. Glenn Beck was still toiling on Headline News. There was no Tea Party or health-care reform. The only climate of hate was the pervasive post-Iraq campaign of vilification of George W. Bush, nicely captured by a New Republic editor who began an article thus: “I hate President George W. Bush. There, I said it.”

Finally, the charge that the metaphors used by Palin and others were inciting violence is ridiculous. Everyone uses warlike metaphors in describing politics. When Barack Obama said at a 2008 fundraiser in Philadelphia, “If they bring a knife to the fight, we bring a gun,” he was hardly inciting violence.

Why? Because fighting and warfare are the most routine of political metaphors. And for obvious reasons. Historically speaking, all democratic politics is a sublimation of the ancient route to power — military conquest. That’s why the language persists. That’s why we speak without any self-consciousness of such things as “battleground states” and “targeting” opponents. Indeed, the very word for an electoral contest — “campaign” — is an appropriation from warfare.

When profiles of Obama’s first chief of staff, Rahm Emanuel, noted that he once sent a dead fish to a pollster who displeased him, a characteristically subtle statement carrying more than a whiff of malice and murder, it was considered a charming example of excessive — and creative — political enthusiasm. When Senate candidate Joe Manchin dispensed with metaphor and simply fired a bullet through the cap-and-trade bill — while intoning, “I’ll take dead aim at [it]” — he was hardly assailed with complaints about violations of civil discourse or invitations to murder.

Did Manchin push Loughner over the top? Did Emanuel’s little Mafia imitation create a climate for political violence? The very questions are absurd — unless you’re the New York Times and you substitute the name Sarah Palin.

The origins of Loughner’s delusions are clear: mental illness. What are the origins of Krugman’s?

— Charles Krauthammer is a nationally syndicated columnist. © 2011, The Washington Post Writers Group.