They may call this the Sunshine State, but the political climate going into Tuesday’s presidential primary was looking plenty stormy Sunday, as the top Republican contenders stepped up their personal attacks on each other.

The increasingly combative Mitt Romney, having opened up a double-digit lead­­ in two new polls, was looking to finish off rival Newt Gingrich with a withering line of assault that characterized the former House speaker as a whiner who has been rendered unelectable by his own questionable ethics.

And Gingrich, desperate to avoid a rout in the biggest primary contest so far, called the former Massachusetts governor both a liar and a liberal.

“I am, in fact, the heir to the Reagan movement, not some liberal from Massachusetts,” Gingrich told a crowd of thousands here at The Villages retirement community.

But it was Romney who claimed momentum as the two leading contenders set off on a final campaign sprint across Florida. An NBC News-Marist poll showed Romney leading Gingrich 42 percent to 27 percent, and a Miami Herald-Tampa Bay Times-El Nuevo Herald poll had Romney with a similar lead, 42 percent to 31 percent.

The poll by the Florida newspapers showed Romney — who lost the primary four years ago to the eventual nominee, Sen. John McCain (Ariz.) — ahead in every region of this vast state, though the race appears closest in conservative northern Florida. Romney was running particularly strong among women, where he enjoyed a 19-point lead; among men, the two were roughly tied.

Coming into this contest after Gingrich’s upset win in the Jan. 21 South Carolina primary, the race between the two had appeared to be a close one.

But Romney enjoys the benefits of superior financial and organizational resources in a state that has 10 media markets.

Romney and his allied “Super PAC” have been blanketing the airwaves with advertising that reminds Florida voters of Gingrich’s stormy tenure as House speaker and his subsequent consulting work for Freddie Mac, the government-backed mortgage giant that some conservatives blame for the financial collapse that hit this state’s real estate market particularly hard.

And in something of a role reversal, Gingrich also faltered in two debates over the past week, while Romney performed aggressively.

Romney said the former House speaker should “look in the mirror” to discover why he is losing ground among Republican voters.

“The people of Florida have watched the debates and listened to the speaker and listened to the other candidates and said, ‘You know what? Mitt Romney is the guy we’re going to support,’ ” Romney told a rally of more than 2,000 supporters in downtown Naples.

Romney chided that Gingrich has been “selling influence in Washington at a time when we needed people to stand up for the truth in Washington.”

Meanwhile, Gingrich again accused Romney of dishonesty. “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 an appearance on ABC’s “This Week.”

Gingrich won the endorsement of former rival Herman Cain over the weekend and will be campaigning with him Monday, in hopes of consolidating grass-roots conservatives behind him.

“This debate is going to go on,” Gingrich said. “It’s going to get clearer and more decisive. And I think what we’re offering is very different. There is a reason that the New York and Washington establishment is opposed to me. I would genuinely change Washington. Romney would manage the decay.”

His anti-establishment message resonates with many of those who are showing up at his rallies.

One of them was Tom Coutré, who was wearing a sweatshirt he got when he took a 1993 course that Gingrich taught at Reinhardt University in Georgia.

Asked why the former speaker appears to be falling behind in Florida, Coutré retorted: “Old establishment money. It’s as simple as that.”

Gingrich pledged that the nominating contest would “go all the way to the convention” and pointed to the fact that he continues to lead in national polls, although that surge came after his win in South Carolina.

Fundraising could also grow more difficult. Gingrich told Bloomberg News that his campaign has about $600,000 left. Meanwhile, it has continued to spend lavishly, including on a luxurious chartered 68-seat Boeing 737.

Romney plans to quickly expand his campaign’s footprint nationally this week, with a campaign swing after Florida’s Tuesday primary through a trio of states — Nevada, Colorado and Minnesota — that hold the next contests.

“I think we’ll have an opponent right to the end,” said Romney senior adviser Eric Fehrnstrom. “It’s everybody’s right as a candidate to stay in, and I don’t think the race will be settled after Florida. I think it goes on after that. I think the calendar in February is very favorable for Mitt Romney because it includes a lot of states he won four years ago — Colorado, Minnesota, Maine, Michigan, Nevada — those are places that Mitt did well in and where he continues to have a strong base of support.”

Meanwhile, former Pennsylvania senator Rick Santorum canceled his Sunday campaign appearances to be with his 3-year-old daughter, Bella, who is hospitalized in Philadelphia. The campaign said Santorum’s five older children, led by eldest Elizabeth, 20, will host a planned rally in Sarasota on his behalf.

And Texas Rep. Ron Paul, who has invested little in the Florida contest, campaigned in Maine, which holds the bulk of its caucuses Saturday. Speaking on CNN’s “State of the Union” Sunday, he vowed to stay in the race despite his focus on small caucus states.

“We’re going to stay in and see what comes of it,” Paul said, acknowledging that he doesn’t have the money to wage a bigger campaign. “It is a rough road competing with establishment money.”

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Staff writers Rosalind S. Helderman and Lisa Rein contributed to this report.