Republican presidential contender Mitt Romney leveled his sights on GOP rival John McCain this weekend as he sought to maintain his shrinking lead in the Granite State.

On the primary trail in Petersborough, N.H, Romney on Sunday poked McCain in the eye over his vote against the Bush packages of tax cuts in 2001 and 2003, as well as for refusing to vote to eliminate the estate tax, known by opponents as the "death tax."

While calling McCain a "good man" and noting they agree on foreign trade, Romney's sharpest points for the Arizona senator were over taxes.

"Right now Senator McCain and I are both battling for your support and your vote. He's a good man but we have differing views on this. He voted against the Bush tax cuts. He voted against eliminating the death tax forever, and so we've got some differing views here," Romney said.

"I believe in pushing taxes down. I also believe in trade around the world and that's a place where Senator McCain and I agree."

McCain's campaign didn't take long to fire back, needling Romney on the tax issue as well as a number of the former Massachusetts governor's recent public relations gaffes.

"Welcome to Mitt Romney's bizarro world, in which everyone is guilty of his sins," McCain adviser Mark Salter said.

Salter continued, saying Romney "didn't support Ronald Reagan. He didn't support President Bush's tax cuts. He raised taxes in Massachusetts by $700 million. He knows John McCain is gaining on him so he does what any small varmint gun totin,' civil rights marching, NRA endorsed fantasy candidate would do: he questions someone else's credibility. "

"New Hampshire is on to you, Mitt. Give it a rest. It's Christmas."

Salter's statement drew its own response from Romney's campaign.

"The McCain campaign's name-calling is neither substantive or relevant to the debate over important issues,"  Romney spokesman Kevin Madden said, adding that his candidate "believes in leadership, not name-calling."

Romney is facing stronger political headwinds lately.

On Sunday, the Concord (N.H.) Monitor published an editorial calling on voters to not vote for Romney, and a new Boston Globe poll shows McCain and Romney in a statistical dead heat: Romney with 28 percent of likely New Hampshire voters; McCain, 25 percent; Rudy Giuliani, 15 percent. The poll of 410 likely GOP voters had a 5 percent margin of error.

Romney's campaign shot back at the Monitor, considering the anti-endorsement a badge of honor.

"Governor Romney has taken firm positions that are at odds with the board's support for drivers licenses for illegal immigrants, their position against school choice and their advocacy for taking 'Under God' out of the Pledge of Allegiance, "Madden said. "The governor happens to disagree with the editorial board on all those issues, as do most Republicans in New Hampshire." 

As for his fellow candidates, Romney has repeatedly stated that he's not attacking them, he's making "comparisons" of his and their positions. But it sure looks like an attack, say some analysts.

"The problem is he's on the verge of becoming a caricature. People are saying this guy flip-flopping, I thought I knew who he was ... as governor of Massachusetts. And now all of a sudden he's a far right Republican," Democratic strategist Garry Mauro told FOX News on Monday,  pointing Romney's switch on key issues like abortion.

"And lashing out and attacking at this late stage over Christmas, that's an inside-the-box thinking, and this is an outside-the-box year for campaigning," Mauro said.

"I think it's a big mistake for Romney to be hitting McCain in this particular way at this particular time," Republican strategist Nancy Pfotenhauer agreed. "He's essentially attacking McCain for holding the line on spending. Every Republican presidential candidate is anti-tax. McCain was just also in favor of smaller government "That type of kind of fast and loose with the record is not going to withstand scrutiny and the people of New Hampshire know John McCain pretty well, and I think they are not going to appreciate this from Mitt Romney."