Rounding out the field of candidates who participated were businessman Herman Cain, Rep. Ron Paul of Texas and Mrs. Bachmann.
Each began with an explanation of his or her first governing principles, then faced a three-member panel. Under questioning from Princeton University professor Robert George, founder of the American Principles Project, each of the candidates predicted naming a pro-life running mate.
Mr. Paul disputed Mr. George’s call to use the 14th Amendment to impose a federal ban on abortion, saying the issue should be returned to the states. Mr. Romney said he would tackle abortion by appointing Supreme Court justices who would overturn the Roe decision.
The Democratic National Committee said the Republican field’s effort to court tea party voters meant candidates were appealing to “the most narrow, extreme and divisive wing of a Republican Party not exactly known for its moderation.”
“Now, one Republican presidential candidate after another is pledging allegiance to the tea party and its extreme economic agenda - an agenda that would double down on the failed Republican policies of the last decade that nearly sank our nation into a second Great Depression,” DNC spokesman Brad Woodhouse said.
In his opening statement, Mr. Romney seemed to give a nod to the political evolution he has made over the years: “The older I get, the more I appreciate the extraordinary brilliance of the founders of this country,” he said.
Mr. Paul, opening his own remarks, said talking about the founders and their principles is not new to him.
“I’ve been trying to do that for 35, 40 years,” he said.
On health care, all of the candidates agreed that the president overreached, but Mrs. Bachmann went the furthest, arguing that the individual mandate in the national law is unconstitutional and that the federal Constitution should prevent states from enacting individual mandates.
“I believe it is also unconstitutional for states to mandate as a consideration of citizenship,” Mrs. Bachmann said. Pressed for where the federal Constitution tied states’ hands on this issue, she stumbled, telling Mr. George that she would turn to him for enlightenment.
Constitutional scholars generally think that states have such compulsory powers, though federal courts are considering whether the federal government does.
Mr. Romney has been heavily criticized by conservatives for signing legislation with an individual mandate for Massachusetts when he was the state’s governor.
On Monday, the former governor said his experience with health care reform in Massachusetts makes him the best candidate to debate Mr. Obama because he can tell the president where he went wrong.
“I’d say to him, ‘Why didn’t you give me a call?’ ” Mr. Romney said.
In addition to missing Monday’s appearance at the South Carolina forum because of wildfires in his home state, Mr. Perry canceled his plans to campaign in California on Tuesday.