COLUMBIA, S.C. — For the Republican presidential candidates who want to stop in South Carolina, it comes down to this: How far are they willing to go?
A day after Mr. Romney’s victory in New Hampshire left his rivals running out of time to block his path to the nomination, he was greeted here by a wave of attacks on his business record, his past support for abortion rights and his character.
With little left to lose, of Texas and their allies sought to portray Mr. Romney as insufficiently steadfast in his conservatism in this very conservative state, threatening a scorched-earth approach to the primary to be held here on Jan. 21.
But there were some signs that a pressure campaign from the party establishment — encouraged and to some degree organized by pro-Romney forces — was forcing his rivals to recalibrate if not rethink the attacks. A growing chorus of high-profile Republicans criticized the attacks on Mr. Romney’s earlier career buying and selling companies as Democratic talking points.
Two days after former of Utah said that Mr. Romney “likes firing people,” The Associated Press reported him as saying on Wednesday: “If you have creative destruction in capitalism, which has always been part of capitalism, it becomes a little disingenuous to take on Bain Capital,” Mr. Romney’s former firm.
But Mr. Gingrich said he would not back off as an outside “super PAC” supporting him introduced a scathing video about Mr. Romney’s work at Bain. And Mr. Perry kept up his critique of what he has called Mr. Romney’s “vulture capitalism.”
It was Day 1 of what is shaping up as a 10-day test of whether conservatives can marshal the arguments, tactics and unity to slow Mr. Romney and rally around a single alternative — and of whether Mr. Romney, now in a commanding position, can show the muscle needed to stamp out the opposition and take control of the party.
Mr. Romney utilized the full force of his formidable campaign machinery to create a backlash against the attacks on his record at Bain. Employing resources no other campaign can match, his Boston headquarters held conference calls with his huge array of endorsers around the nation, sent talking points to supporters and enlisted go-betweens to tell leaders of the pro-Gingrich group Winning Our Future that they were harming the party with the attacks.
At the very least, Mr. Romney’s team appeared to have made headway in casting his opponents as abandoning their own party’s longstanding support for the free market. It received backing Wednesday from two political voices that have had the respect of the Tea Party movement here in ways Mr. Romney has not: Gov. Nikki R. Haley of South Carolina, who has endorsed Mr. Romney, and Senator Jim DeMint, who has not.
“I am baffled by the fact that we are putting the free market on trial here,” Ms. Haley said in an interview on Wednesday. “I’m concerned for my party. The free market’s what we fight for.”
Speaking on “The Laura Ingraham Show,” Mr. DeMint lectured Mr. Gingrich: “Newt, you’re a great American. Get back on your positive focus. Talk about your big ideas.” He singled out Mr. Gingrich’s attacks on Mr. Romney for changing his position on abortion, saying, “This idea of condemning people who change their minds is not a good idea for any of us.”
It was potentially critical cover in a state where Mr. Romney’s past positions in favor of abortion, and his Mormon religion, could tilt important evangelical voters against him. Mr. Romney seemed to try to get out ahead of the possibility that evangelical voters might spurn him based on his Mormonism, saying on MSNBC on Wednesday morning that he was not running for “pastor in chief” and emphasizing the economy and national security.
Those comments came as national evangelical leaders prepared to meet in Texas this weekend to consider backing one of Mr. Romney’s rivals, and his campaign was on guard for any movement to coalesce behind an alternative to him.
In the morning, Mr. Romney had declared the attacks against his business background a failure. But later, with others taking on his opponents for him, Mr. Romney did not mention the subject when it came time to address supporters here Wednesday evening. He kept his focus instead on President Obama.
The spirited new phase of the campaign was on full display here; on a Christian radio station, a commercial for Rick Santorum informed listeners that he had home-schooled his children, supported anti-abortion legislation and called for “all conservatives to unite.” Ron Paul’s campaign was showing an advertisement attacking Mr. Santorum for “a record of betrayal” on federal spending.
But it was Mr. Gingrich and the “super PAC” supporting him, Winning the Future, that was being watched most carefully. With millions of dollars behind it from the casino magnate Sheldon Adelson, it was poised to have as big an effect on Mr. Romney as any other opposing force.
At a private meeting of Mr. Romney’s national finance committee on Wednesday morning, Senator John McCain helped make the case that it was time for Republicans to begin gathering around Mr. Romney’s candidacy and pushing back against the attacks from Mr. Gingrich, Mr. Perry and other rivals.
But the pro-Gingrich group’s leaders did not seem to be shaken by that or by more direct pressure on them to cease and desist.
“We’re not going to back off an inch,” said a senior adviser to the group, Rick Tyler, who took issue with the accusation from Mr. Romney’s supporters that his group was “attacking capitalism.”
“This isn’t about attacking capitalism,” Mr. Tyler said. “This is about Mitt Romney’s record on jobs, but more importantly, it’s about who is best qualified, given their records, to create jobs in South Carolina.”
The Republican pressure came from all sides. A voter approached Mr. Gingrich in Spartanburg, S.C., and said that he, too, opposed Mr. Romney. But he pleaded for him to “lay off the corporatist versus the free market” language.
While Mr. Gingrich said, “I agree with you,” he sought to draw the distinction that his criticism was not an attack on capitalism. His spokesman followed up with a statement that he did not intend to soften his stance, which he made clear in a message to supporters.
“There’s no more time for talking about stopping Mitt Romney,” the message said. “We’re going to do it next week in South Carolina or he’s almost certain to be the Republican nominee, whether conservatives like us want it or not.”
Richard A. Oppel Jr. contributed reporting from Lexington, S.C.