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One of the most contested states in presidential politics is center stage Sunday night as FOX News airs a Republican candidates primary debate in Orlando, Fla., that is sure to be used by the 2008 contenders as a chance to cater to the party's conservative base.

It's also an opportunity for the eight candidates — Kansas Sen. Sam Brownback dropped out of the contest on Friday — to build on the varying strengths they are seeking to project.

"I think the most important thing these candidates can do tonight is really show the Republican base that they are sort of Ronald Reagan conservatives. That's what they claim to be, but that's what they need to show," said Aubrey Jewett, a political scientist at the University of South Florida.

Watch the Republican presidential candidates primary debate live on FOX News Channel and FOXNews.com at 8:00 p.m. ET.

Sen. John McCain led the way in attempts at image-building, telling "FOX News Sunday" that while he still supports campaign finance reforms widely panned by conservatives, he has the most compelling record when it comes to national security, limited spending and leadership.

"I have a consistent conservative voting record for more than 20 years, and those are graded by different organizations — the National Taxpayers Union, Citizens Against Government Waste. Certainly, on national security, I have the knowledge and experience and background, and so I'm the only one that saved the taxpayers $2 billion when I was able to defeat the effort to have an Air Force tanker that cost $2 billion more than it should have and people went to jail," he said.

Countering the claims to executive credentials often put forth by opponents Mitt Romney and Rudy Giuliani, McCain added that as the former commander of the largest squadron in the United States Navy, he doesn't need any on-the-job management training.

"And I didn't run it, I led it. It was tens of millions of dollars of assets, training brave young Americans to go fight and defend the country. I'll defend my leadership of a 1,000-men and -women organization with the management of anything that anybody else has done," McCain said.

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The Arizona senator added that he understands that his campaign has made mistakes, particularly on a key issue for conservatives — immigration reform — and he knows now from listening to voters that border security must precede measures to deal with the estimated 12 million illegal immigrants in the U.S.

"I got the message, we're going to secure the borders," he said.

But Mike Huckabee is also building on his image as the conservative candidate with executive experience, and can now fall back on a straw poll taken at the Values Voters Summit held in Washington, D.C., this weekend. The online portion of the poll gave Romney a slight edge, but among guests attending the conference, Huckabee won the field of GOP candidates with 51 percent of the vote.

The former Arkansas governor noted that his success in the poll sponsored by the Family Research Council topped a similar vote in Fort Lauderdale, Fla., a few weeks ago and the Palmetto Family Council straw poll in South Carolina.

"When the voters who consider themselves values voters are actually given the opportunity, overwhelmingly, I win those contests. And I think it is becoming clearer and clearer that this part of our party and our country wants somebody who is a hard-working, consistent conservative with some authenticity about those convictions," Huckabee told "FOX News Sunday."

Huckabee, a Baptist minister, said he's not the only conservative in the race, but he is the most consistent and the one that is moving steadily up in the polls.

"I think we need to be careful when you see candidates who are better at lip-syncing the songs than singing it from their hearts," Huckabee said. "I'm a conservative that hasn't had but one position on a lot of key issues, whether it's sanctity of life, the Second Amendment, the Bush tax cuts, whether it's — gosh, the position of traditional marriage."

"Nobody's going to find some YouTube moments of me saying something radically different than what I'm saying today," he said in a veiled slap at Romney.

With the script seemingly set for Sunday evening's debate, the rest of the GOP pack is also trying to prove its credentials to the base. Each of the candidates has a position to spin. For Romney, who actually won the online straw poll at the Values Voters Summit, he is likely to say that he is the candidate with momentum.

Speaking on CBS' "Face the Nation" on Sunday, Romney said he is pleased to welcome the endorsement of Bob Jones III, chairman of the board at Bob Jones University, despite Jones saying that he finds Romney's Mormonism an "erroneous faith."

"I'm not expecting him to endorse my faith. I'm not asking anyone to do that. I'm asking him to look at me as an American and judge my values, learn about me and my family, my character, and decide whether I could help America at a critical time. And I'm pleased that you have an evangelical Christian leader who says, look, Mitt Romney is a guy who is a social conservative, an economic conservative, a foreign policy conservative. Those three branches, if you will, of conservatism have to be united if we're going to win the White House," Romney said.

Added for good measure, Romney later said: "There's no question that the older I get the smarter Ronald Reagan gets."

Fred Thompson is likely to say his campaign is not lackluster or lagging behind despite the emerging perception among GOP insiders. The former Tennessee governor must build on a sluggish performance at the Values Voters Summit, in which he spoke for only a few minutes, and then a second appearance on Saturday night for Florida Republicans that some in attendance called embarrassing.

"I'm proud to say that I went to Congress as a consistent conservative. For eight years in the United States Congress, I voted to cut taxes, to balance the budget, for welfare reform, for less regulation and for judges who would follow the law and the Constitution and not make it up as they go along," Thompson told the assembly in an eight-minute speech that left guests wanting more.

"A lot of high expectations, but he didn't seem to have the energy people would have liked and they were very disappointed," Susan McManus, a political scientist at the University of Central Florida, said of Thompson's performance.

Among the frontrunners, Giuliani may have the most difficult task in trying to sell himself as a conservative. But the highly recognizable former New York City mayor leads the national polls, is considered by many GOP voters the most formidable candidate to take on Sen. Hillary Clinton should she be the Democratic nominee and has the inside track for the endorsement of Florida Republican Gov. Charlie Crist, who is very popular right now.

"I come to you today as I would if I were your president, with an open mind and an open heart, and all I ask is that you do the same. Please know this. You have absolutely nothing to fear from me," Giuliani told guests at the Values Voters Summit. He again scored big on Saturday with Florida voters attending the Presidency IV convention that preceded Sunday's debate at the Rosen Shingle Creek Resort in Orlando.

Florida Republican Party Chairman Jim Greer said not only do the candidates have to project themselves as able to beat Clinton, they must be responsive to concerns central to Republicans.

"They have to hit on the issues that are important to everyday citizens, that they need to talk about what voters want to hear, not some rhetoric," Greer said.

Whether the top-tier Republicans — or the other candidates, House Reps. Duncan Hunter, Tom Tancredo and Ron Paul — make any inroads with voters on Sunday night will depend not only on their degree of conservatism, but possibly how many viewers they can tear away from the deciding game in the American League championship series between the Boston Red Sox and the Cleveland Indians.

FOX News' Carl Cameron, Major Garrett and Neil Simon contributed to this report.