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MIAMI — Newt Gingrich slammed GOP rival Mitt Romney on Sunday for the steady stream of attacks he likened to "carpet-bombing," trying to cut into the resurgent front-runner's lead in Florida in the dwindling hours before Tuesday's pivotal presidential primary.
Surging ahead in polls, Romney kept the pressure on Gingrich with a dominant advertising presence that questioned the former House speaker's leadership and ethics. During campaign stops, Romney divided his focus between Gingrich and President Barack Obama.
In what has become a wildly unpredictable race, the momentum has swung back to Romney, staggered last weekend by Gingrich's victory in South Carolina. Romney has begun advertising in Nevada ahead of that state's caucuses next Saturday, illustrating the challenges ahead for Gingrich, who has pledged to push ahead no matter what happens in Florida.
Romney's campaign has dogged Gingrich at his own campaign stops, sending surrogates to remind reporters of Gingrich's House ethics probe in the 1990s and other episodes in his career.
Gingrich reacted defensively, accusing the former Massachusetts governor and a political committee that supports him of lying, and the GOP's establishment of allowing it.
"I don't know how you debate a person with civility if they're prepared to say things that are just plain factually false," Gingrich said during appearances on Sunday talk shows. "I think the Republican establishment believes it's OK to say and do virtually anything to stop a genuine insurgency from winning because they are very afraid of losing control of the old order."
Gingrich objected specifically to a Romney campaign ad that includes a 1997 NBC News report on the House's decision to discipline Gingrich, then speaker, for ethics charges.
After hounding Gingrich during two debates last week, Romney returned more of his attention to Obama, who had been Romney's chief target as he tried to make the case that he was the most worthy Republican to challenge the Democratic incumbent.
But Romney didn't relent in swiping at Gingrich, even as an NBC News/Marist poll published Sunday showed Romney with support from 42 percent of likely Florida primary voters, compared with 27 percent for Gingrich.
"He's now finding excuses ... complaining about what he thinks were the reasons he thinks he's had difficulty here in Florida. But you know, we've got a president who has a lot of excuses," Romney said at a rally in Naples. "And the excuses are over, it's time to produce."
Former Pennsylvania Sen. Rick Santorum, trailing in Florida by a wide margin, stayed in his home state, where his 3-year-old daughter, Bella, was hospitalized. She has a genetic condition caused by the presence of all or part of an extra 18th chromosome. Aides said he would resume campaigning as soon as possible.
Texas Rep. Ron Paul, who has invested little in Florida, looked ahead to Nevada. The libertarian-leaning Paul is focusing more on gathering delegates in caucus states, where it's less expensive to campaign. But securing the nomination only through caucus states is a hard task.
The race began moving toward a two-person fight in South Carolina, and has grown more bitter and personal in Florida.
The intense effort by Romney to slow Gingrich is comparable his strategy against Gingrich in the closing month before Iowa's leadoff caucuses Jan. 3.
Gingrich led in Iowa polls, lifted by what were hailed as strong performances in televised debates, only to drop in the face of withering attacks by Romney, aided immensely by ads sponsored by a political committee run by former Romney aides.
In Florida, senior Romney aides have popped up at Gingrich events to question Gingrich's conservative credentials. Led by Romney's top Iowa adviser, David Kochel, Romney's team cites Gingrich's criticism of House Budget Committee chairman Paul Ryan's Medicare overhaul plan last year, and his appearance with then-House Speaker Nancy Pelosi, D-Calif., in an advertisement supporting climate-change legislation.
"That kind of language emboldens the critics of conservatism," Kochel said. "We're out pointing that out correcting the record."
Gingrich has responded by criticizing Romney's conservative credentials. Outside an evangelical Christian church in Lutz, Gingrich said he was the more loyal conservative on key social issues.
"This party is not going to nominate somebody who is a pro-abortion, pro-gun-control, pro-tax increase liberal," Gingrich said. "It isn't going to happen."
But Gingrich, in appearances on Sunday news programs, returned to complaining about Romney's tactics, rather than emphasizing his own message as that of a conservative with a record of action in Congress.
"When we get to a positive idea campaign, I consistently win," Gingrich said. "It's only when he can mass money to focus on carpet-bombing with negative ads that he gains any traction at all."
Romney and the political committee that supports him had combined to spend some $6.8 million in ads criticizing Gingrich in the Florida campaign's final week. Gingrich and a group that supports him were spending about one-third that amount.
Gingrich worked to portray himself as the insurgent outsider, collecting the endorsement of tea party favorite Herman Cain, whose own campaign for president foundered amid sexual harassment allegations.
It was unclear how aggressively Gingrich would be able to compete in states beyond Florida. The next televised debate, a format Gingrich has used to his advantage, is not until Feb. 22, more than three weeks away.
Romney already has campaigned in Nevada more than Gingrich, is advertising there, and stresses his business background in a state hard-hit by the economy. His campaign welcomed the Sunday endorsement of the Las Vegas Review-Journal, Nevada's largest newspaper.
Michigan and Maine, states where Romney is well-positioned also hold their contests in February. Arizona, a strong tea-party state where Gingrich could do well, has its primary Feb. 28.
Associated Press writers Steve Peoples in Naples and Shannon McCaffrey in Lutz contributed to this report.