Forget Dennis Kucinich's claims about seeing UFOs. The new unsolved mystery of the campaign trail is the "whisper."

The blogosphere was abuzz Friday morning over an audible whisper that cut through the mix during the GOP presidential debate in Boca Raton, Fla., the night before.

It's unclear who it was, but the voice could be heard after moderator Tim Russert asked Mitt Romney whether, as a fan of Ronald Reagan, he would "do for Social Security what Ronald Reagan did in 1983."

Right before Romney answered, somebody seemed to whisper: "He raised taxes."

And then Romney responded, as if taking the cue, "I'm not going to raise taxes."

So where did the whisper come from?

A fellow candidate? A techie? An earpiece? Brian Williams? (Williams was also moderating.)

The former Massachusetts governor didn't appear to be wearing any kind of wire or earpiece - but bloggers and those who comment on their Web sites are scratching their heads over where the voice came from.

Web site The Raw Story wrote in a brief article about the incident Friday that some are accusing Romney of "shenanigans" - like waiting for a prompt before answering the question.

The Romney campaign has not yet responded to a request for comment from FOX News.

Jeremy Gaines, a spokesman for debate sponsor MSNBC, said in an e-mail to FOXNews.com, "We heard the same thing you heard. There was obviously an open mike which picked up the whisper, but we have no way of knowing who did the whispering."

The whispers about the whisper are reminiscent of the Internet speculation in 2004 over whether George W. Bush was wearing a wire during a debate, after photos showed what appeared to be an unusual bulge on his back.

Bush denied he was getting a feed from his aides, and laughed off the rumors.

Click here to see the YouTube video of the whisper at the GOP debate in Florida.