By John Whitesides
TAMPA, Florida (Reuters) - It seems a natural assignment for Chris Christie, the bombastic, in-your-face New Jersey guy whose confrontational style as the Republican governor of a liberal state has made him a rising political star.
Christie, who gives the keynote speech at the Republican convention on Tuesday, may not be used to being an opening act but he is perfectly comfortable delivering the red-meat rhetoric that fires up conservative activists.
And when he lays out Republican presidential contender Mitt Romney's case for a change in leadership from President Barack Obama, he will take a big step into the national spotlight with implications for his own potential White House bid in 2016 or 2020.
As a Republican in Democratic-dominated New Jersey, Christie has been forced to reach out to independents while cultivating a pugnacious style that makes him a hero to some national conservatives.
Romney hopes that double-edged appeal rubs off. Criticized as cold and cautious, he has not gained ground on Obama in polls since clinching the nomination in the spring - he now runs about even or slightly behind - and he had not fired up conservatives until he chose another of their favorites, Congressman Paul Ryan, as his running mate earlier this month.
"Conventions are about rallying the troops and also about presenting your opening message to the broader public, and Christie can do both," said David Redlawsk, director of the Rutgers/Eagleton poll in New Jersey.
"He has great appeal to the Republican rank and file but he can walk the middle ground when he has to," Redlawsk said. "He's the tough guy who can tell it like it is, and it's very valuable to Romney to have him in that role."
Republican strategist Rich Galen likened Christie's speech to the tough-talking and highly praised 2008 debut of vice presidential nominee Sarah Palin - she had convention-goers roaring but eventually became a controversial figure who turned off many independents.
"With Christie, you get all the energy of a Sarah Palin speech without all the side issues," Galen said. "He'll blow the roof off the place, and that's what the Romney people are looking for."
Christie said he had no intention of softening his signature sarcastic tone, and had not been asked to do so by Romney's team.
"I don't think he picked me hoping I would show up and be somebody else," Christie told reporters in New Jersey. "I don't think they have any expectation, nor have they requested that I have a personality-economy."
Christie's effectiveness as an economic messenger has been undercut recently by a slumping New Jersey economy that has shed jobs and now has the fourth-highest state unemployment rate, 9.8 percent, higher than the national average of 8.3 percent.
The so-called "Jersey Comeback" previously trumpeted by Christie has begun to ring hollow.
"There are three words that are not in my speech on Tuesday night: The Jersey Comeback," he told state reporters. "Those three words aren't in, and were never in."
Giving a convention keynote speech is no guarantee of future political success. Few remember Democratic Senator Mark Warner's 2008 speech, or former New York Mayor Rudy Giuliani's Republican address that year.
But Obama's memorable 2004 speech catapulted the little-known Illinois state legislator into public view, and the high-profile slot is a vote of confidence from Romney to Christie that could pay off in future races.
"It's not the end-all if it isn't the best speech in the world," said Ron Bonjean, a Republican strategist. "But a great speech will be a great benefit for him in the long run."
Christie had a prolonged spell of indecision last year as he pondered making his own presidential run, only to drop the idea and endorse Romney early in what became a heated nominating battle.
Some conservatives in New Jersey and nationally have criticized him for holding too-moderate views on social issues like guns and immigration.
A June Rutgers/Eagleton poll of New Jersey voters put Christie's favorability rating at 50 percent, his highest since taking office in January 2010.
"This is a guy who is a Republican in a very Democratic state, and he still manages 50 percent favorability, so he must be doing something right," Redlawsk said.
"And what he's doing is appealing to the middle ground people because Democrats consistently dislike him intensely," he said. "He is a very polarizing figure here."
Christie's reputation for abrasiveness has grown amid repeated high-profile showdowns with state public employee unions, state judges he calls liberal activists and a Democratic-controlled state legislature that has resisted his plans to cut spending and taxes.
A proliferation of YouTube videos of his public confrontations with reporters and voters helped spread his image as a straight-talking tough guy, and his substantial girth - the subject of countless jokes on late-night television - made him seem an angry everyman.
Steve Lonegan, a conservative who ran against Christie in the Republican primary for governor in 2009, said he had a mixed record on economic issues but had done an admirable job of battling the state's predominant Democrats.
"There is a limit to what a Republican governor can accomplish in New Jersey, which has a Democrat-controlled legislature that follows the drumbeat of Obama's policymakers," said Lonegan, who is now the state director of Americans for Prosperity, the advocacy group founded by billionaire conservative brothers David and Charles Koch.
"But in spite of that he has made progress, and that's a message the rest of the country needs to hear," he said.
Redlawsk said Christie's myth, fueled by national media fascination with his angry style, sometimes surpassed his accomplishments.
"The truth is, as usual, far more complex. To the extent he has accomplished specific things he set out to accomplish, it's been because the Democratic majority in the legislature was working on those things already," he said.
(Editing by Alistair Bell and Mohammad Zargham)