Jonah Goldberg‘s latest column explores the president’s argument that Republican challenger Mitt Romney wants to “double down on the same trickle-down policies” — meaning tax cuts — that led to the recent economic crisis.

This is Obama’s core message. In one way or another, he says it all the time. It’s his kicker on the stump. You cannot watch an interview with the president or one of his subalterns without hearing it.

And yet, I don’t think I’ve ever heard a TV interviewer, host, or pundit ask, “What are you talking about?”

Finally, the Washington Post’s “fact-checker,” Glenn Kessler (not exactly a darling of the political Right), tackled it recently. He found that it’s a lie, giving it three “Pinocchios” out of four. He also found that the Obama campaign has virtually no citations to back up the claim. The supporting material for the ad quoted above cites a single column by the Post’s liberal blogger, Ezra Klein, who told Kessler: “I am absolutely not saying the Bush tax cuts led to the financial crisis. To my knowledge, there’s no evidence of that.”

Klein is right. So is Kessler. “It is time for the Obama campaign to retire this talking point,” Kessler concluded, “no matter how much it seems to resonate with voters.” He would have given it the full four Pinocchios save for the fact that Obama occasionally throws in “deregulation” along with “tax cuts” as part of the explanation. In its defense, the Obama camp says it means all of Bush’s policies, not just the tax cuts it harps on almost exclusively — never mind that even Obama admits Bush issued more regulations than he did.