Fox News host Bill O’Reilly did a nice job last night of challenging Rep. Michele Bachmann’s claim that the woes of Republicans stem from their portrayal in the media. “Let’s face it, over 80 percent of all the the messaging regarding conservatives in media is negative, and so this is not surprising. It’s a fact; we have to deal with it,” claimed Bachmann.

On most Fox News shows, such a characterization of the media would have drawn a round of high-fives. Yet O’Reilly wasn’t letting it get past him. He noted that even the “liberal media” has been “pounding” Obamacare over the past month or so. “You would think that the Republicans would benefit from that,” protested O’Reilly.

The congressowman said that people across the country are “upset on every level because their lives haven’t improved.” That said, she proclaimed: “Again, 80 percent of media reporting is anti-conservative,” Bachmann insisted, sticking with her statistic.

Not for the first time, Bachmann failed to cite an authoritative source for the number. The Erik Wemple Blog has sampled studies showing that newsrooms lean liberal or Democratic in convincing numbers but doesn’t recall such a precise percentage attached to the aggregate work of the media. That would be a monster undertaking fraught with mounds of methodological problems. How, for instance, do you define media for such a measurement? How do you define “anti-conservative”? So we punted the question to Tim Graham, an official with the Media Research Center who’s been watchdogging the mainstream media for decades. If anyone out there has heard of this 80 percent number, it’s Graham.

Here’s how he responded when asked about Bachmann’s contention: “It sounds like a guesstimate, not a real statistic. I’m not familiar with it. I’d be more comfortable saying 80 percent of journalists are anti-conservative, but that’s a guess. I loved the 1992 number when 89 percent said they voted Clinton, 7 for Bush. I often joked that was it was probably more like 95 to 3.”

We’ll stay on this Bachmann-80 percent thing.