As the Republican convention kicks off Tuesday in Tampa, one niggling question remains: who is the mystery speaker with a prime time slot just before Mitt Romney accepts the presidential nomination.

Aides to the Republican White House hopeful have taken far too much pleasure in teasing frustrated journalists and heightening the sense of intrigue. "Tune in!" campaign strategist Russ Schriefer challenged in his latest update.

The schedule released by the Republican National Convention lists a "To Be Announced" speaker on Thursday night just before the keynote introduction by Hispanic rising star Marco Rubio and Romney's all-important acceptance speech.

With most party heavyweights already securing spots during three nights of heady political theater 10 weeks out from the November election, speculation was rife that the mystery person could be a notable absentee.

Former presidents George and George W. Bush have both said they won't be attending, although a video from the pair is set to play on Wednesday's program.

This would be the first convention by either party since Jimmy Carter didn't show up in 1996 -- apparently his invitation was late and he declined -- that wasn't attended by a current or former president.

Former vice president Dick Cheney has also said he will not be in Tampa, but the architect of the Iraq war and the "war on terror" is hardly flavor of the month in the current Republican Party.

Perhaps the biggest Republican celebrity not due to attend is former Alaska governor Sarah Palin, who lit up the 2008 convention as John McCain's surprise running mate with her talk of hockey moms and lipstick.

Her barnstorming convention performance was credited with giving McCain a significant bounce in the polls, but her later policy gaffes contributed to the ticket's downfall.

A surprise 2012 convention appearance by the Tea Party favorite would certainly be a show-stopper, but pundits considered it highly unlikely as it would risk overshadowing Romney's big moment.

Perhaps the mystery speaker is a Hollywood celebrity or a famous Olympian. Maybe it will just be an ordinary, humble American with a stirring personal message. If it is a cruel joke by the Republican Party, the media will vent.

Who knows? Tune in!