TAMPA, Fla. -- The Republican National Convention is abuzz with speculation over the identity of a mystery speaker who's supposed to appear Thursday night.

Convention officials have refused to reveal who will fill the "To Be Announced" slot on the closing-night schedule, but the list of possibilities being generated by convention delegates and observers stretches from Hollywood (Clint Eastwood) to hologram (Ronald Reagan) to a handful of conservative favorites who fall somewhere in between.

Republican National Committee Chairman Reince Priebus refused to give even the smallest hint Wednesday.

"Everyone's going to have to tune in on Thursday night and check it out," he told Fox News.

Rumors were flying on the convention floor Wednesday afternoon that Hollywood icon Eastwood is the surprise guest, the speculation fueled by reports of the actor and director's travel plans.

Eastwood was supposedly headed to Tampa on Wednesday, but nobody in the party would confirm whether the Academy Award winner was going to speak or just hang out.

Whoever the surprise speaker is, he or she will appear after "American Idol" winner Taylor Hicks and before Sen. Marco Rubio of Florida.

Delegates to the Republican convention, meanwhile, are guessing wildly.

Former Republican presidential candidate Michele Bachmann told The Washington Examiner she discussed the mystery with her daughters and they all voted for New York Jets quarterback Tim Tebow, whose public displays of faith have made him a hero of sorts among Christian conservatives.

"Tim Tebow is a very real guy, a gracious man," Bachmann, a delegate from Minnesota, told The Examiner. "I hope he is our mystery man Thursday night. There are a lot of good picks, but he'd be mine."

Some delegates were pinning their hopes on an appearance by Ronald Reagan. Though the conservative icon died in 2004, some suggested he could appear as a hologram, as the late rapper Tupac did during the Coachella music festival in April.

Rep. Tom Price, R-Ga., said he'd rather see Reagan's wife, Nancy.

"I'd love to see the first lady," Price said. "Nancy Reagan would be wonderful to see."

Comedian and Republican activist Victoria Jackson said the convention doesn't need help from Hollywood. It would be much better served by a rousing speech from Sarah Palin, the Tea Party's most popular conservative, she said.

Palin brought down the house at this year's Conservative Political Action Conference in D.C., Jackson noted, and could do the same here in Tampa.

"She's on fire," Jackson said. "That's the passion we need here."