Megyn Kelly debuted her new evening show, The Kelly File, on the Fox News Channel on October 7th of this year.
That night, the O'Reilly Factor, at the 8PM time slot, attracted 2.589 million viewers. With the the size of O'Reilly audience being a potential lead-in to Megyn's show at the 9PM slot, Kelly only managed to hold 2.066 million. The following night, Megyn managed to hold 2.767 million of the 2.978 million watching O'Reilly; a difference of only 211,000 viewers. But, every night since, Megyn's audience has grown slowly. For example, look at last Thursday's ratings from the ZAP2it website:
I think O'Reilly will at some-point lose his prime-time title. I personally don't watch the show anymore because I can't take the constant "set-up" of confrontations and his overall arrogance. Having followed his ratings in the past, O'Reilly's 8PM slot used to consistently attract 3 to 3.4 million viewers on a regular basis. But now, more often than not, his viewership is under 3 million; as noted in the second paragraph above.