In writing The Republican Brain , I had a problem to solve. You see, it was one thing to cite all the psychological research  suggesting that liberals and conservatives just think differently, because they have different personalities and cognitive styles. Sure, one could infer on this basis that certain conservatives, especially authoritarian conservatives , would simply be more factually wrong about certain deeply held beliefs. But I also needed evidence from the real world showing that, you know, conservatives or Republicans are more factually incorrect.
That’s where all the fact-checker data  came in.
You see, we have paid professionals whose job it is to track just how wrong Democrats and Republicans are. They’re called fact-checkers, and as I show in The Republican Brain (and in this article  for The Nation), both PolitiFact and the Washington Post’s fact-checker column  do indeed rate Republicans significantly worse than Democrats overall. The data for PolitiFact had already been analyzed before I did the book (see here ); I then carried out, with the help of a research assistant named Aviva Meyer, a similar analysis of 315 fact-checks by The Washington Post from 2007 through 2011. And the punchline is the same: Republicans fare worse than Democrats, especially when it comes to the worst ratings (4 Pinocchios, "pants on fire").
I find these fact-checker data particularly compelling, by the way, for the following reason: Neither PolitiFact nor Glenn Kessler (who writes the Post’s column), think of themselves as liberal partisans. To the contrary, I would argue that both go too far in trying to ding Democrats and liberals, just to make themselves appear balanced (and, presumably, to keep getting their calls returned by the other side of the aisle). Therefore, if their data shows Republicans fare worse, that really says something.
Indeed, I was so convinced of these fact-checkers' need to hug the center that I expected Kessler to try to course correct in the wake of my analysis showing that he rates Republicans worse than Democrats. I figured he would try to ding Democrats a little more, so as to even the score a bit and appear less biased.
It now appears that I was wrong in that assumption. Kessler--a thoroughly honest guy, there's no disputing that--has now extended the dataset  across the first six months of 2012. And he finds, lo and behold, numbers just like mine. More specifically, Kessler gets the following:
In the past six months, we had 80 Fact Checker columns that rated Republican statements, for an average rating of 2.5 Pinocchios, compared to 56 that rated statements of Democrats, for an average rating of 2.11.
My overall finding for 2007-2011 was 2.45 (Republicans) to 2.12 (Democrats). In other words, I’m on precisely the same page with Kessler, data-wise.
And the data are all the more striking in that I believe Kessler inflates the Democrat total, intentionally or otherwise. Take, for instance, this March 2012 item  in which Kessler gives President Obama a 4 Pinocchio rating, the worst possible, because he used a dubious quotation from Rutherford B. Hayes in a speech. I’m not saying the quotation was legit—but one of Obama’s sources was, after all, the Encyclopedia Britannica! The point is, errors like this happen all the time, but if the 4 Pinocchio rating is to retain any meaning, it can't be used on such pecadilloes. 4P ratings should be reserved for major, repeated lies with political consequences—like, for instance, the Republican denial of global warming .
And indeed, if you want evidence that Kessler dings Democrats and lets Republicans off easy, consider the following comparison. While Obama gets 4Ps over Rutherford B. Hayes, Kessler did not even give a rating  to Sarah Palin for her incredible historical whopper about Paul Revere having "warned the British." In the latter case, I think 4 Pinocchios was fully merited, because Palin doubled down on the obvious falsehood--and because it was highly ideological in nature, and not just silly.
So in light of all this, to see Kessler still rating Republicans worse than Democrats really, really says something to me.
What does Kessler make of the data on his own ratings? Here’s what he writes:
…we still think the slightly higher average for Republicans is mostly due to the primary season.
In fairness, however, we should note that writer Chris Mooney, in an article for The Nation  in May, counted up all of the ratings of The Fact Checker since its inception in 2007 and concluded that in general Republicans received a higher average Pinocchio rating than Democrats. (Out of a total of 315 ratings, he calculated an average of 2.12 for Democrats and 2.45 for Republicans.) He argues that this means Republican politicians are more often “egregiously wrong;” others might suggest this demonstrates some sort of liberal bias.
We respectively disagree with both analyses. The result is that both parties end up with an average above Two Pinocchios, which under our rating scale means “significant omissions and/or exaggerations.” That’s the big picture. Surely our politicians can do better than that. The record on both sides is pretty lousy, and neither side should feel good about their performance. [Ital added]
I’m sorry, but this strikes me as poor reasoning on Kessler’s part. We have a clear statistical difference between the ratings bestowed on Republicans, and the ratings bestowed on Democrats, over a long period of time. And given that the Pinocchio scale only goes from 1 to 4 (there is no zero, and no half Pinocchios are given), a difference of about .3-.4 over time is not a small one.
What's more, given that this difference does not appear to be a fluke, there has to be a reason for it to exist. And I agree, one could posit many explanations: Maybe there is a selection bias with respect to which items are being rated. Maybe Kessler himself is biased against Republicans. Or—my theory—maybe Republicans just are inherently more untruthful. (To explain why that’s the case, one could then come up with additional competing explanations.)
But the point is, there has to be an explanation. It just won’t do to say, as Kessler does, that since both Dems and Republicans score above Two Pinocchios, both ought to be ashamed of themselves. The data are telling us something more than that—something stronger than that.
In my opinion, what they're telling us is that Republicans today are simply more untruthful than Democrats--and the difference is dramatic enough that even a centrist-leaning fact checker, who strives to be non-partisan, cannot fail to pick it up.