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Mitt Romney made a broad appeal to voters in his speech on faith and politics Thursday, pledging to serve no one religion if he is elected, while at the same time stressing the importance of religious liberty and defending his right to worship as a Mormon.

Romney made the speech in an attempt to answer skepticism about his religion. But he only made brief specific references to Mormonism, underscoring instead what he called the "common creed of moral convictions” shared by Americans and the value of the nation's "symphony of faith."

“Freedom requires religion just as religion requires freedom,” Romney said. “Freedom and religion endure together, or perish alone.”

As John F. Kennedy did 47 years ago in a speech answering questions about his Catholic faith, Romney insisted that his religion would not dictate his duties in office if elected president. Romney referenced Kennedy in his opening lines.

"I do not define my candidacy by my religion. A person should not be elected because of his faith nor should he be rejected because of his faith ... I will put no doctrine of any church above the plain duties of the office and the sovereign authority of the law," Romney said. " If I am fortunate enough to become your president, I will serve no one religion, no one group, no one cause, and no one interest ... A president must serve only the common cause of the people of the United States.”

Romney delivered the address at the George H.W. Bush Presidential Library in College Station, Texas. The former president introduced the former Massachusetts governor, though the introduction was not an endorsement of his candidacy.

In an attempt to assuage concerns of evangelical Christians and southern Baptists, Romney pivoted the half-hour address on clearly establishing the lines between his personal faith and the responsibilities of public office. But he said his convictions would "inform" his presidency.

"I believe in my Mormon faith and I endeavor to live by it. My faith is the faith of my fathers. I will be true to them and to my beliefs. Some believe that such a confession of my faith will sink my candidacy. If they are right, so be it. But I think they underestimate the American people," he said. "Americans do not respect ... believers of convenience. Americans tire of those who would jettison their beliefs, even to gain the world."

And Romney criticized what he called an attempt to take the notion of separation of church and state well beyond its original intention, complaining that some seek to remove any recognition of God from the public domain.

"It is as if they are intent on establishing a new religion in America — the religion of secularism. They are wrong," Romney said, to strong and lasting applause.

Romney also said that having to outline his religion to win the post of president is unconstitutional.

"No candidate should become the spokesman for his faith. For if he becomes president he will need the prayers of the people of all faiths," he said.

The top-tier GOP hopeful and his aides stressed beforehand that the address would not be a “primer on Mormonism." And they insisted the speech is not a response to slipping polls or anti-Mormon literature on the trail. But it's a topic he's been repeatedly forced to confront.

The speech has been rumored for months and has been a cause of division among Romney's staff.

Romney told FOX News Tuesday that he didn't feel pressured to give the talk, but that he wanted to address "the need to preserve the pluralistic religious heritage of America."

While 16 members of Congress are Mormon, including Senate Majority Leader Harry Reid, Romney acknowledges his religion is more of an issue because he is running for president. If elected, he would be the first Mormon in the Oval Office.

He's already run into distrust on the campaign trail. In November, voters in early election states reported receiving phone calls from people who appeared to be pollsters but then made critical comments about Romney's faith. At the time, Romney said, "The attempts to attack me on the basis of my faith are un-American."

The faith-based skepticism is widespread. A FOX News poll of 900 registered voters released in October found that only 36 percent of those polled thought most Americans would feel comfortable with a Mormon president. Twenty-one percent said Romney's faith made them less likely to vote for him. Twenty-six percent said they did not think Mormons were Christians.

A Pew Research Center poll in September found a quarter of all Republicans said they would be less likely to vote for a Mormon.

Mainstream Mormonism holds that authentic Christianity vanished a century after Jesus and was restored only through Joseph Smith, considered a prophet in the Mormon faith.

Perhaps feeling scrutinized about his religion, Romney stumbled over a question on the Bible during a debate in Florida last week.

After stammering in his response to whether he believes the Bible is literal or figurative, Romney said, "The Bible is the word of God. I mean, I might interpret the word differently than you interpret the word, but I read the Bible and I believe the Bible is the word of God. I don't disagree with the Bible. I try to live by it."

He began writing the Faith in America speech the day after the debate, at the Hilton in Boca Raton.

Romney stressed Thursday that he believes "Jesus Christ is the son of God and the savior of mankind," but explained that his beliefs about Christ differ with those of followers of other faiths.

He also made the speech to the backdrop of what he called the threat of "theocratic tyranny." At the beginning and end of the address, he referenced the danger posed by radical Islam.

Romney is addressing the issue head on just as religion takes a lead role in the Republican race, particularly in early voting Iowa where Romney’s chief competitor, Southern Baptist Minister Mike Huckabee, has jeopardized Romney's once comfortable lead.

A Des Moines Register poll taken from Nov. 25 to 28 showed Huckabee with 29 percent and Romney with 24 percent. The poll’s margin of error was 4.4 percent.

Huckabee is riding a tide due in large part to support from Christian conservatives, who make up anywhere from 30 to 50 percent of Republicans who traditionally attend the Iowa caucuses, set for Jan. 3. Huckabee has only amplified the issue of religion, calling himself a Christian leader in television ads.

FOX News' Shushannah Walshe and Carl Cameron and The Associated Press contributed to this report.