Many of us in the econ biz were wondering how the new leaders of Congress would respond to the sharp increase in American economic growth that, we now know, began last spring. After years of insisting that President Obama is responsible for a weak economy, they couldn’t say the truth — that short-run economic performance has very little to do with who holds the White House. So what would they say?

Well, I didn’t see that one coming: They’re claiming credit. Never mind the fact that all of the good data refer to a period before the midterm elections. Mitch McConnell, the new Senate majority leader, says that he did it, that growth reflected “the expectation of a new Republican Congress.”

The response of the Democratic National Committee — “Hahahahahahaha” — seems appropriate. I mean, talk about voodoo economics: Mr. McConnell is claiming not just that he can create prosperity without, you know, actually passing any legislation, but that he can reach back in time and create prosperity before even taking power. But while Mr. McConnell’s self-aggrandizement is funny, it’s also scary, because it’s a symptom of his party’s epistemic closure. Republicans know many things that aren’t so, and no amount of contrary evidence will get them to change their minds.

At least Mr. McConnell didn’t do what many of his colleagues have done when faced with inconvenient facts: resort to conspiracy theories.