Until recently, professor Jane Hall was a regular guest on the O'Reilly Factor, debating conservative Bernie Goldberg. She's left Fox, and as she explained to CNN's Howard Kurtz (10/25/09), she never considered herself a liberal anyway:

KURTZ: When you appeared regularly on O'Reilly, were you there as a token from the dreaded MSM?

HALL: Well, I was there as a defender of the MSM. And you wouldn't believe how many famous journalists I talked to, who said better you than me. Let me tell you my side of the story. They didn't want to come on. It is hard to do, because it was like, when did you quit beating your wife? That was usually the question. But I felt it was worth doing.

KURTZ: Do you consider yourself a liberal?

HALL: No.

KURTZ: You were paired with Bernie Goldberg, the conservative point of view, who wrote a book about the media's slobbering love affair with Barack Obama?

HALL: Right.

KURTZ: So was that a fair pairing, to have someone who has that point of view, and you? You consider yourself a journalist.

HALL: I consider myself a journalist. I'm now able to say opinions because I'm a professor. I consider myself a moderate. In that universe, I was probably considered a wacky professor by O'Reilly. He would sort of pat me on the head and say, now, Jane, I know you liberals feel this way. And I'd say, I'm not really a liberal. So, yes, there's not necessarily a left/right comparison on there.