NEW YORK — The Republican presidential race has become a no-holds-barred contest over character.
With the pace of the GOP contest quickening, Mitt Romney and Rick Perry are resorting to tough language online and while campaigning to undermine each other's credibility and values.
"It's time for you to tell the truth," Perry said during last week's Republican debate, all but calling the former Massachusetts governor a liar.
The Texas governor also is trying to cast Romney as someone who lacks a core set of beliefs, highlighting Romney's shifts on health care and other issues in hopes of dislodging him from atop the field.
Romney is portraying Perry as a dimwitted novice who coddles illegal immigrants and takes liberties with his economic record.
"The great challenges we have we will overcome," Romney said in South Dakota recently, "if we have leaders that will tell the truth, and live with integrity, and who, by virtue of their life experience, know how to lead." It was a suggestion that Perry didn't fit that bill.
The amped-up rhetoric signals a more aggressive phase in the race and sets the tone in the 10 weeks before the nominating contest begins in Iowa in early January. It also illuminates campaign strategies and previews likely attack ads sure to surface on television soon.
It's raised concerns among some Republicans, who fear a drawn out, personal battle between their top contenders will only help President Barack Obama's chances of winning next year.
"I don't like that, I'm not for that. I'm a Ronald Reagan Republican, he didn't think it was smart to attack each other and I don't either," oil billionaire T. Boone Pickens told Fox News last week after Romney and Perry got in each other's faces during the Las Vegas debate.
Despite their oft-stated reverence for Reagan, the two leading Republican hopefuls are ignoring Reagan's so-called 11th commandment: "Thou shalt not speak ill of any fellow Republican."
Romney, seen as the Republican to beat, has identified Perry as his top rival, even with businessman Herman Cain polling well and lower-tier contenders such as Newt Gingrich and Rick Santorum drawing positive buzz in debates.
Only Perry has been able to compete with Romney in fundraising and the two are expected to have enough resources for a protracted national campaign if necessary. Both have the backing of powerful special political action committees that can raise unlimited funds to run attack ads of their own.
Romney's campaign has started web site, , that jabs at Perry's record in Texas. The Romney team posted a video on the site after Perry's stronger-than-usual debate performance last week, stringing together several clips from past debates in which Perry stammered and looked confused. www.careerpolitician.com
"Ready to lead?" the ad asked.
The Romney campaign pulled the video after CNN complained it used too much of the network's material without permission. Still, the ad signaled a chief Romney argument going forward – Perry isn't up to the job of being president.
Also last week, Romney's campaign released another web video trying to debunk Perry's claim that Texas leads the nation in job creation, which is the central premise of Perry's candidacy. The video asserts that unemployment in the state has gone up under Perry and that most of the new jobs created were in state government or went to illegal immigrants.
The ad includes a clip of Perry saying he disagrees with those figures.
"Disagree? It's a fact," the ad states – essentially calling Perry a liar.
Perry has used Romney's own record on illegal immigration to suggest that he's disingenuous.
During the debate, Perry pointed out that Romney had used a lawn company at his Massachusetts home that employed illegal immigrants. Perry's campaign followed up with a web vide, arguing that Romney was a hypocrite on illegal immigration, health care and his own political ambition.
"You can't lead a nation by misleading the people," the video concludes.
Perry made the same point at a campaign event, describing himself as a conservative "authentically, and not by convenience."
He added: "You won't hear any shape-shifting nuance from me."
Perry got an assist this past week from the Obama campaign and its allies, who have singled out Romney.
Obama campaign manager Jim Messina echoed the flip-flopper theme, telling reporters Romney will "say and stand for anything to get elected, even if it means forgetting the positions he's previously taken."
Priorities USA Action, a super PAC run by two former Obama White House aides, released a web video that needles Romney for his wealth and suggesting he believes millionaires like him should pay a lower tax rate than middle-class Americans.
The ad drew a rebuke from Romney spokeswoman Gail Gitcho, who called it "another pathetic attempt by President Obama's political machine to distract attention from their nonexistent record on creating jobs."
Democrats have their own history of nasty primaries, most recently between Obama and Hillary Rodham Clinton in 2008. The two reconciled after months of personal attacks, and Clinton now serves as secretary of state.
Ken Khachigian, a Republican strategist and former Reagan White House staffer, said he finds the character attacks between Perry and Romney "unpleasant to watch" but said such primary dust-ups were inevitable."Party politics, like all politics, is rough and tumble," Khachigian said. "When it's all over, the desire to defeat Obama will be so huge they'll all be sipping tea together."RELATED VIDEO: