I don't know. It's this generation's version of Deep Throat.
I suspect, although I could be all wet, it probably came from a journalist who became disenchanted with the coverage of Obama over the last 2 years - from campaign to presidency.
NRO wants Carlson to release all the emails, right now. In principle, I agree with that. But, I also understand that Carlson wants to drive traffic to his site, and the longer he can milk it, the better.
Conservatives need a counter point to HuffPo, which makes money hand-over-fist. If this helps the Daily Caller, so be it.
Brietbart said he was out bid for it...so the assumption is Carlson paid someone. Andrew had originally offered 100K for a list. AB mentioned this on Hugh Hewitt though at the time all he would was its big news and as big as anything he had seen and that a competitor had out bib him for the list