Top Romney advisors claim they have been left in the dark about a mystery speaker who may address the convention on Thursday night.

"I do not know. I'm intrigued," Eric Fehrnstrom, a senior advisor to Romney, told ABC News' Jonathan Karl and Yahoo! News David Chalian amid laughter at the ABC News/Yahoo! News breakfast in Tampa Monday morning. "I had not heard that that there was going to be a mystery speaker, no."

Other top members of Romney's team - senior advisor Beth Myers, director of advertising Ashley O'Connor, and pollster Neil Newhouse - also claimed ignorance about a surprise guest speaking Thursday evening.

The latest schedule released by the Republican National Convention Monday lists a "To Be Announced" speaker slated to speak just before Sen. Marco Rubio and the presumptive GOP nominee Mitt Romney. A number of Olympians, including Michael Eruzione, Derek Parra, and Kim Rhode, and senior advisor Bob White are expected to speak Thursday evening.

So who could the mystery speaker be? A number of political heavyweights - including former Florida Gov. Jeb Bush, New Jersey Gov. Chris Christie, former presidential candidate Newt Gingrich, former Secretary of State Condoleezza Rice, and former presidential candidate Rick Santorum - have already secured spots earlier in the week, and Romney's wife, Ann, will speak Tuesday night.