The former Massachusetts governor, front-runner in the race for his party’s nomination to oppose President Barack Obama in 2012, promised at the annual “Values Voter Summit” he would oppose marriage rights for homosexuals.

But, Romney, who is viewed skeptically by conservatives for his past support for abortion rights and gay rights, kept to a relatively moderate line as he advocated “civil and respectful debate” on contentious social issues.

The speaker who immediately followed Romney took veiled shots at the candidate’s religion and said only an “authentic” Christian should be US president.

Some evangelicals question the validity of Romney’s Mormon faith, which they do not consider a form of Christianity.

“Poisonous language does not advance our cause,” Romney said. .”.. The blessings of faith carry the responsibility of civil and respectful debate. The task before us is to focus on the conservative beliefs and the values that unite us — let no agenda narrow our vision or drive us apart.”

Romney appeared to be responding at least partly to comments to reporters by Texas pastor Robert Jeffress describing Mormonism as a cult. Jeffress, pastor of the 10,000-member First Baptist Church in Dallas, introduced Republican candidate and Texas Governor Rick Perry at the conference on Friday.

Perry’s campaign rejected the pastor’s views on Mormons. “The governor does not believe Mormonism is a cult,” said Perry spokesman Mark Miner.

Romney was one of five Republican presidential hopefuls to make a pitch for support at the influential gathering of social and religious conservatives who play a big role in the party’s nominating race.

All of the Republican candidates describe themselves as conservative, and all of the leading contenders agreed to address the conference.

The summit is sponsored by the Family Research Council, American Family Association and other evangelical Christian groups.

While calling for the US Supreme Court to overturn the Roe v. Wade decision that legalized abortion, Romney said the issue should be decided by the states and acknowledged “strong convictions” on both sides.

“It speaks well of our country that almost all Americans recognize that abortion is a problem. The law may call it a right, but no one ever called it a good,” Romney said in a speech focused on his economic and foreign policy proposals.

Romney was followed to the stage by Bryan Fischer, a director of the American Family Association, who is known for inflammatory remarks against homosexuality and “non-Christian religions,” which he has said include Mormonism.

“The next president of the United States needs to be a man ... of sincere authentic genuine Christian faith,” he said.

In fiery remarks, Fischer demanded that the next US president reject the theory of evolution, stop government assistance for the poor, veto any increase in the debt ceiling and “treat homosexual behavior not as a political cause at all, but as a threat to public health.”

He spoke out strongly against Islam, calling the religious faith the greatest long-term threat to US liberty.

“Every single mosque in America is a potential recruiting or training cell for Islamic terror,” Fischer said.