CONCORD, N.H. - Mitt Romney's Republican presidential rivals piled on the criticism Sunday, two days before New Hampshire's primary, with a combative Newt Gingrich accusing the front-runner of "pious baloney" and charging him with hiding behind inaccurate attack ads.

Time was running short Sunday to curtail the former Massachusetts governor here and perhaps elsewhere. Romney's opponents started the day assailing him on the debate stage and ended it by doing the same in appearances across New Hampshire and South Carolina. They worked to appeal to those Republican voters unenthused with the idea of Romney as the party's choice to challenge President Barack Obama in November.

Romney fired back at Gingrich, the former speaker of the House of Representatives during a morning debate and by evening, he also had taken shots from former Pennsylvania Sen. Rick Santorum, former Utah governor and first ambassador to China Jon Huntsman and former Texas Gov. Rick Perry.

Santorum made a beeline to the conservative upstate of South Carolina to trumpet the endorsement of former Republican presidential candidate Gary Bauer. There, he alluded to Romney's position switches on a series of issues, saying: "We've got a lot of candidates that just adapt to whatever the environment is .... I don't, because the truth doesn't change."

Looking to revive his flagging candidacy, Perry also swooped into the Southern state. The Texas governor told roughly 300 people at a restaurant in Spartanburg that his campaign, after a disappointing finish in the Iowa caucuses, was like the last stand at the Alamo. He cast Romney as an insider.

"We've got to have somebody that is an outsider that is not interested in tinkering around the edges -- but that will go into Washington, D.C., and overhaul that place," he said.

Back in New Hampshire, Gingrich assailed Romney as a "Massachusetts moderate" and promoted a video being released by his allies that attacks Romney's business career. The Gingrich-leaning Winning Our Future PAC said Sunday that a 28-minute online video -- which assails Romney for "reaping massive awards" while head of Bain Capital -- may show up on TV in the coming weeks.

Romney, the former Massachusetts governor, won the Iowa caucuses last Tuesday by a scant eight votes over Santorum but is so far ahead in New Hampshire polls that his rivals have virtually conceded he will win.

South Carolina comes next, on Jan. 21, the first Southern state to hold a primary. While it is the contest where Gingrich, Santorum and the rest of Romney's rivals face an urgent need to slow his candidacy, Romney noted that he has been endorsed by that state's governor, Nikki Haley.

Santorum finished second in Iowa, followed by Texas Rep. Ron Paul, with Gingrich fourth, Texas Gov. Rick Perry fifth and Minnesota Rep. Michele Bachmann in last place. She has since quit the race.

Huntsman, the former Utah governor, skipped Iowa in hopes of a breakout showing in New Hampshire.

He was mobbed at a coffee shop in Hampstead, where he stood on the counter to defend his past service in the Obama administration and assail Romney.

"I put my country first," he said. "Apparently Mitt Romney doesn't believe in putting country first. He's got this bumper sticker that says ... Believe in America. How can you believe in America when you're not willing to serve America? That's just phoney nonsense."