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?