By Andy Sullivan
WASHINGTON, Aug 20 (Reuters) - Donald Trump will play a "surprise" role when the Republican Party kicks off its national convention next week in Tampa, Florida, a party official said on Monday.
The real estate mogul and reality-television star is scheduled to participate in a to-be-revealed fashion on the first day of the four-day convention, where Republicans are to formally nominate former Massachusetts Governor Mitt Romney to face Democratic President Barack Obama in the Nov. 6 election.
Trump's appearance could be an intriguing sideshow at a convention where Republican officials hope to counter Democrats' efforts to cast Romney as a millionaire who is out of touch with middle-class Americans.
Trump will be featured on a day when the evening's headline speaker will be Romney's wife, Ann, who often has been deployed by the Romney campaign to portray a more personal side of a candidate who can seem dispassionate and distant.
Trump briefly topped opinion polls when he said he was exploring a presidential run in the spring of 2011, but he drew widespread ridicule for advancing discredited theories questioning whether Obama was born in the United States, and therefore eligible to be president.
The self-promoting Trump has since emerged as one of Romney's most colorful supporters.
"I am doing something that is going to be, I think, really amazing; it'll be great," Trump said last week on the Fox Business Network. "We'll see what happens. We'll see how it's received."
Trump is not listed as one of the official speakers on Aug. 27, the first day of the convention, but he will participate, a Republican official confirmed.
"There will be a surprise," the official said.
The time of Trump's appearance on Aug. 27 is unclear. A schedule that Republicans released Monday indicated that showing diversity within the party will be a priority during the evening session, the prime viewing time for the national TV audience.
Besides Ann Romney, other female speakers that night include South Carolina Governor Nikki Haley and U.S. Representative Cathy McMorris Rodgers of Washington state. Republicans are scrambling to erode Obama's advantage among women voters.
Kentucky Senator Rand Paul, a favorite of the anti-tax, limited-government Tea Party movement and son of Representative Ron Paul, another contender for the Republican nomination, also speaks on Monday. Rand Paul's participation appears to be an olive branch of sorts to his independent-minded father, who has not formally ended his campaign.
Former Obama ally Artur Davis, who like the president is African-American, will reprise a now-standard role at Republican conventions: the Democratic politician who has grown disillusioned with his party.
A former Alabama congressman who was among Obama's earliest supporters in the 2008 presidential race, Davis opposed many of Obama's signature policies - such as the president's healthcare overhaul - during a failed bid for governor of Alabama.
Like Georgia Senator Zell Miller in 2004 and Connecticut Senator Joe Lieberman in 2008, both former Democrats, Davis is expected to argue that the Democratic Party has moved too far to the left.
Other speakers on Aug. 27 include U.S. House of Representatives Speaker John Boehner Of Ohio, Florida Governor Rick Scott and Ted Cruz, who is seeking a U.S. Senate seat from Texas.
Republicans will announce schedules for the remaining days of the convention this week, party officials said.