The cliché: In a blog post today, The New York Times' Ross Douthat says Rick Perry's "heat-packing, convict-executing, treason-accusing persona makes him seem like the perfect embodiment of the current right-wing id." On that point, he seems to have found consensus. Jonathan Chait writes in The New Republic, "His total liberation from the constraints of reason give Perry a chance to represent the Republican id in a way Romney simply cannot match." Jim Newell at Gawker says "Rick Perry cannot be real. He is the ultra right wing conservative id." Ezra Klein writes in The Washington Post, "Perry is a credible incarnation of the conservative id." Id, indeed.
Where's it from: Most basically, they refer to Sigmund Freud's theory that structures the psyche into the id, the ego, and the super-ego. The id, according to Merriam Webster, "is completely unconscious and is the source of psychic energy derived from instinctual needs and drives for the part of our personality that acts on instinct and ego." It's often used by non-psychologists to talk about a person who acts with knee-jerk convictions and animal instinct, a person who is a lot like Rick Perry, as it turns out. "Conservative/Republican id" has been floating around as a phrase for a long time though rarely has it been so unanimously applied to one politician. Regarding Rick Perry, Douthat today seems to be quoting none other than Ross Douthat. His Aug. 14 column in the Times predates all the previously quoted uses and seems to be the first prominent reference to "Rick Perry as id". Arguing against Perry's electability, Douthat wrote, "He's the conservative id made flesh, with none of the postpartisan/uniter-not-a-divider spirit that successful national politicians usually cultivate."
Why it's catching on: Rick Perry seems to have two main qualifications for embodying the conservative id. First, he seems the most instinctively, not conveniently, conservative. In this, he stands apart in peoples' minds from main-rival Mitt Romney. Second, he seems to "act on instinct and ego," as the dictionary entry for id says, with quick-draw statements that get him into hot water. We've all seen the list written out many times: "Treasonous," "Ponzi scheme," "Galileo."
Why else: It's worth noting that while "liberal id" isn't a totally unused phrase, it's much rarer to see it than its rival twin. (And when it is, it's also only applied to fearsome people on the left: Howard Dean and Frank Rich, for example.) Though Douthat who started the Perry-id talk trends rightward, most of those who picked up the phrase are liberal writers. Just the idea of "conservative id" speaks to a judgement liberals have for conservatives they fear or dislike -- That they act too quickly, don't think very hard, and leave aside the more reasoned, analytical parts of their psyche. The Freud reference is tickling when you consider that conservatives so often accuse liberals of being too "cerebral."