BURLINGTON, Iowa -- Are Newt Gingrich’s attacks on Mitt Romney about to go over the top?

That was the buzz Tuesday morning after Gingrich flat-out called Romney a liar on a morning talk show -- and as he continued to escalate his rhetoric about the former Massachusetts governor on a final day of campaigning before evening caucuses begin across Iowa.

U.S. Republican presidential candidate and former U.S. House Speaker Newt Gingrich takes questions from voters at Elly's Tea and Coffee in Muscatine, Iowa Jan. 3, 2012. (JEFF HAYNES/REUTERS)

Gingrich addressed midsized crowds in Muscatine and Burlington before lunch Tuesday, making a last-ditch pitch to improve his standing in Iowa and ramping up his barbs against Romney as well as President Obama. Gingrich was worlds more energetic than he’s been the last few days, evidence of just how debilitated he was by the flu he’s been fighting.

In a midday interview on Fox News, Gingrich accused Romney of “negative, vicious politics.” He also said he’s unconcerned that he’s not on the air yet in New Hampshire, South Carolina or Florida: “We’re just getting started,” he told reporters after a mini-town hall at the Drake Restaurant overlooking the Mississippi River in Burlington.

“Figuring out what the core contrast is for the next 30 days is the most important thing we’re doing right now. I’m less concerned about the first wave of ads than I am about getting the strategy right. I’m fairly convinced that we will have a strategy that Romney will find very hard to deal with.”

Gingrich also said he’s still hoping for a better-than-expected finish in Iowa Thursday. “I’m looking forward to tonight to see if we can literally smile our way through the negativity,” he said.

The reality is that the “positive” message that he promised to stick with -- about his history bringing change to Washington, his fealty to Ronald Reagan and supply-side economics -- has been drowned out by the attacks against him.

“I kind of don’t like that deal with Freddie Mac,” said Don Roberts, 58, from Burlington, who said he is leaning toward Gingrich after listening to him Tuesday but has been affected by some of the messages in the ads. “We need a change, but I’m not sure Newt’s the guy to do that.”

But Roberts is even less likely to vote for Romney, he said: “He’s got way, way too much money to relate to a common person like me. I’m a commercial fisherman on the Mississipi River. As long as I’ve got gas in my boat and the river’s flowing, I’m happy.”

An independent super PAC supporting Romney, Restore Our Future, has been pummeling Gingrich with negative ads for weeks -- accounting for, Gingrich regularly states, more than 40 percent of all political ads in Iowa in recent days. Gingrich has been hinting for days that it’s time to fight back. This week, that message has evolved into a flat-out promise to go on the air and tell voters what’s wrong with Romney, too.

“There’s nothing more dangerous than a politician with nothing left to lose,” said Alex Castellanos, a Republican strategist who supported Romney in 2008 but has remained neutral in this campaign. “He thinks Mitt Romney has wronged him. Remember -- this is the guy who suggested that not getting a seat on Air Froce One precipitated a government shutdown. I think he’s going straight to New Hampshire, where Mitt Romney and Romneycare live, and I think he’s going to try to set the record straight.”

One huge question is how much money Gingrich has to exact his revenge -- if that is, indeed, what he’s planning. His spokesman, R.C. Hammond, said Tuesday that Gingrich raised $9.6 million in the fourth quarter of 2011. But it’s not clear how much the campaign spent to raise that money; much of the donations came through direct-mail solicitations, which are costly.

It’s also not clear how much money the independent super PAC working on Gingrich’s behalf, Winning Our Future, has ready to spend. PAC spokesman Rick Tyler, a former Gingrich aide, said, “Well, I don’t know,” when asked when and if the PAC would launch TV ads in the states with primaries queued up after Iowa -- New Hampshire, South Carolina and Florida. But Tyler confirmed that “there’s definitely a shift afoot” in strategy, presumably a reference to Gingrich’s decision to return Romney’s fire with fire.

Tyler wouldn’t say how much money the PAC’s got, but as if to preview the messages against Romney to come, he said: “We’re getting money from true believes in America who don’t want to see a liberal northeastern establishment be our nominee.”

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