Raise Taxes?!

If any of you were watching the Jan 4th Republican debate in FL, you may have caught this little clip. After Mitt Romney's question, you very clearly hear someone whisper "raise taxes" or "he raised taxes". The internet (and our living room) was abuzz after this trying to figure out if it was a moderator, another candidate, or someone in the control room. At other points during the show, we heard paper moving and note-taking, so someone's mic being a problem.
A couple theories are being thrown around on this one. Of course, the Democrats and even Ron Paulbots are convinced this is a cue from one of Romney's guys. This isn't entirely far fetched, considering his response. My first thought was that the tone was sarcastic, leading me to believe Brian Williams had uttered it. That would be in character for him if you've ever seen him off the Nightly News. He's a pretty funny guy, and if he did say it, I'm sure he didn't expect his mic to be on. MSNBC, the network hosting the debate, released this blog which concludes an audience member was responsible for the whisper. (Read it here.)
MSNBC's conclusion seems to be the least reasonable, considering the mic several times picked up the sounds of paper and writing. The sounds were not frequent enough to be a journalist and were far too frequent for any audience member. It was usually during the response to a question as if the moderators had thought of a follow up and jotted it down, or a candidate was taking notes for their rebuttal. If anyone saw the whole debate, let me know your thoughts. It's still in my DVR =)