On the last day of the 2012 Republican National Convention in Tampa, shortly before GOP presidential nominee Mitt Romney takes the stage to accept the nomination, a "to be announced" speaker will be giving some remarks.

Speculation has run rampant as to who "to be announced" will be. The most popular choice on Twitter: a Ronald Reagan hologram.

Whoever is "to be announced," they will be the third to last speaker at the convention, followed by rising Republican star and U.S. Sen. Marco Rubio and Romney.

The Caucus blog run by the New York Times is using the hashtag #RNCmystery to track Twitter user's guesses of who the mystery speaker will be.

By far, the most popular response has been a holographic version of Reagan akin to the Tupac hologram that wowed audiences at this year's Coachella Music Festival in Indio, Calif.

Others mentioned former President George W. Bush, but W has long said he'll be a no-show at the convention (which actually provides perfect cover for being the mystery speaker).

Sarah Palin's name has also been floated, although the mystery speaker is unlikely to be her for the same reasons Bush is not a real possibility -- she'll turn off the independent voters Romney needs to beat President Barack Obama.

Romney's former primary foe, U.S. Rep. Ron Paul, R-Tex., is in the mix as well. However, the Texas congressman passed up on a speaking role at the convention because he didn't want the Romney camp vetting his speech, The Hill reported.

Clint Eastwood is one of the choices being mentioned by Twitter users. But the actor, although he's a Republican, is not well-liked among conservatives due to his narrating of the controversial "Halftime In America" ad run by Chrysler during this year's Super Bowl. The advertisement, a not-so-subtle reference to the auto bailouts, was seen as a thinly-veiled endorsement of Obama.

On the other hand, Eastwood has smoothed things over with the GOP. He has been a fervent supporter of Romney, helping the former Massachusetts governor raise $2 million at an Idaho fundraiser, Reuters reported.

Will The Great Communicator be communicating at the convention in hologram form? Only time will tell.