With the official kick-off to the 2012 primary election season less than four months away -- the leading Republican candidates for president are intensifying their attacks on each other.

Speaking at the Iowa Credit Union League on Friday, Texas Gov. Rick Perry, the national frontrunner, took the sharpest jabs yet at his chief rival, former Massachusetts Gov. Mitt Romney.

Perry told assembled credit union conventioneers the best way to protect the economy is to repeal the president's health care mandate and socialized medicine.

"It failed miserably, whether it was in Western Europe or in Massachusetts," he said in a clear shot at Romney’s health care program that the president said was a model for his initiative.

Perry also returned fire at Romney for, in Monday’s debate, comparing Perry’s job creation record in a state that is rich with natural resources, especially oil and natural gas, to being dealt four aces in a poker game.

"I was the son of tenant farmers. I wasn't born with four aces in my hand," Perry said Friday in a veiled reference to Romney's family wealth.

Polls have shown Perry to have been unscathed among Republican Party faithful by his remarks that Social Security is a Ponzi scheme. But it could potentially damage him in a general election.

A USA Today Gallup poll released Friday finds 30 percent of independent voters are less likely to support the Texan because of the Ponzi scheme remark. Perry re-iterated his opinion Friday - first expressed in the debate - that Social Security will be preserved. "We will fix the Social Security system so it will be there for our young workers," he said.

Michele Bachmann campaigned in California on Friday, attempting to regain the momentum that peaked during her Iowa Straw Poll win in August.

At Monday’s debate, she appeared close to succeeding when she attacked Perry for issuing an executive order requiring teenage girls in Texas to be vaccinated against HPV, a sexually transmitted disease that causes cervical cancer.

But the favorable attention that her response drew took an about face when Bachmann told Fox News that a crying woman informed her after the debate that the vaccine caused mental retardation in her daughter.

According to the Centers for Disease Control, there is no linkage between the HPV vaccine and retardation, nor any other health problem, other than redness around the injection site and the occasional mild fever that is typical of many vaccines.

Bachmann, though, remains skeptical -- against all available scientific evidence. Bachmann says she's not a doctor or a scientist but added there are still "dangerous consequences associated with the vaccine."

Doug McKelway joined Fox News Channel (FNC) in November 2010 and serves as a Washington-based correspondent. Click here for more information on Doug McKelway