Bill O'Reilly's ratings record streak among the coveted group of cable viewers between the ages of 25 and 54 has just been broken, not by a rival network, but by his Fox News colleague Megyn Kelly. Thanks to Fox's GOP primary debate, Kelly's average audience in that key demographic surpassed O'Reilly's in the third quarter of the year. O'Reilly has been #1 on cable in the demo every quarterly period since 2005. His dethroning might create some tension in the halls at Fox, but it's not as if Kelly's gains are coming at his expense. To the contrary, Kelly's 9...