Palin to try to silence media storm in debut

* Palin works on big speech to convention

* Republicans testify to McCain's character

* Bush passes Republican leadership to McCain

By John Whitesides, Political Correspondent

ST. PAUL, Sept 3 (Reuters) - Sarah Palin has dominated the Republican convention for days without making a public appearance but on Wednesday she takes the spotlight with a prime-time speech that will introduce her to American voters.

Since John McCain made the nearly unknown Palin his No. 2, the Alaska governor has been at the center of a media storm fueled by disclosures about her unmarried teenage daughter's pregnancy, a probe into her role in an Alaskan official's firing and questions about the her political record.

McCain, 72, an Arizona senator, and Palin will be nominated by the convention on Wednesday to face Democrat Barack Obama and his vice presidential running mate, Joe Biden, in the Nov. 4 presidential election.

Palin's anti-abortion and pro-gun record have excited conservatives and party activists, but the appearance on Wednesday will be her first chance to directly tell American voters her life story and philosophy.

It comes just five days after McCain shocked the U.S. political world by introducing the 44-year-old first-term governor as his running mate at an Ohio rally.

"She made her first impression on Republicans in Ohio on Friday when McCain introduced her," said Fergus Cullen, chairman of the New Hampshire Republican Party. "Now she can make a first impression on the rest of the country."

Palin, the first female Republican vice presidential nominee, has stayed out of the public eye in Minnesota for two days while the revelations about her family and her record in Alaska surfaced.

She has been preparing her address with speechwriter Matt Scully, who drafted her speech in Ohio. "We're just going to rock 'em, sock 'em -- we kind of like it when people underestimate us," a McCain campaign official said of the speech.

Her speech, when she will accept the nomination, may give the public a chance to assess her familiarity with domestic and foreign policy issues. She will possibly address the issue of her 17-year-old daughter's pregnancy and the investigation into whether she abused her power in having a public safety commissioner fired in Alaska.

PASSING THE TORCH

The furor over Palin has raised questions about McCain's judgment and the depth of investigation that preceded her selection, and could put a dent in McCain's efforts to build momentum heading out of the convention.

As the convention was under way on Tuesday, a peaceful march on behalf of poor people by more than 1,000 demonstrators led to a brief confrontation of some of them with police. Pepper spray and teargas were used to drive the protesters away from the downtown Xcel Energy Center where the convention was being held.

Much of Monday's convention schedule was delayed by Hurricane Gustav's assault on the Gulf Coast, but the gathering resumed on Tuesday with criticism of Obama and testimonials to the character of McCain, a former prisoner of war in Vietnam.

"I'm here to support John McCain because country matters more than party," said former vice presidential nominee Joe Lieberman, a Connecticut senator who ran as Democrat Al Gore's No. 2 in 2000.

Lieberman was defeated in a Democratic primary for his U.S. Senate seat in 2006 over his support for the Iraq war, but won election later that year after qualifying for the ballot as an independent.

"John McCain's whole life testifies to a great truth: being a Democrat or a Republican is important. But it is not more important than being an American," Lieberman said.

The convention also marked the passing of leadership in the party from President George W. Bush to McCain. Bush praised McCain, his rival in a bitter presidential nominating battle in 2000.

"He's not afraid to tell you when he disagrees. Believe me, I know," Bush told the convention in a brief speech via satellite from Washington.

Former Tennessee Sen. Fred Thompson, whose own presidential bid fell short this year, contrasted Obama's speech to 200,000 cheering Germans in Berlin in July with McCain's global reputation for leadership.

"The respect he (McCain) is given around the world is not because of a teleprompter speech designed to appeal to American critics abroad, but because of decades of clearly demonstrated character and statesmanship," Thompson said.

Thompson blasted "Washington pundits and media big shots" who have been critical of Palin.

"The selection of Governor Palin has the other side and their friends in the media in a state of panic. She is a courageous, successful reformer, who is not afraid to take on the establishment," he said.

(Editing by Patricia Wilson and Jackie Frank)