More and more Republican candidates are showing a willingness to step on the so-called third rail of American politics, openly calling for changes in Social Security benefits as the federal government strains to reduce its debt. 

Each Republican who dares bring up the possibility of privatizing accounts or raising the retirement age is invariably hammered by his or her opponent as trying to steal from seniors. But while some have backed down, several big-name Senate candidates are unapologetic in pushing for serious changes to the entitlement program. 

Kentucky Republican Senate nominee Rand Paul was the latest to make waves when he said during a debate on "Fox News Sunday" that "there will have to be changes for the younger generation," specifically talking about the 55 and younger crowd. 

"You're going to have to have eligibility changes for the younger people," Paul said. 

The comment drew an immediate retort from Democratic opponent Jack Conway's campaign, which blasted out a statement as soon as the debate aired accusing Paul of looking to reduce benefits. "Rand Paul does not share Kentucky values," the campaign said. 

Paul's campaign counterpunched, accusing Conway of alluding to a similar plan in 2002. 

The rapid-fire exchange was typical in a campaign season where Social Security is a popular talking point, but no less toxic than previous election years. 

The Social Security clash hit the airwaves in Florida on Tuesday after Gov. Charlie Crist's independent Senate campaign released a TV ad accusing GOP nominee Marco Rubio of wanting to "balance the budget on the backs of seniors" by cutting benefits and raising the retirement age. 

"Charlie Crist is against raising the retirement age," the ad said. "He'll protect Social Security because our seniors have earned it." 

Rubio's campaign responded with a statement from former Gov. Jeb Bush accusing Crist of "purposely trying to scare seniors in order to win votes." The statement said Rubio "will protect Social Security" and will not support reductions for current retirees or those close to retirement. 

But Rubio does support changes to the entitlement program for younger generations. He has often repeated points from a March debate on "Fox News Sunday" in which he said for those "many years away from retirement," raising the retirement age "has to be on the table." 

"That's got to be part of the solution, the retirement age gradually increases for people of my generation," he said. 

Rubio told Fox News in September that he does not favor privatizing the system but repeated that changes will have to be made for "future beneficiaries." 

Social Security began in 1935 as a means to help elderly people suffering during the Depression. Turned into a retirement account system, Social Security taxes take 12. 4 percent of income for individuals earning up to $102,000. 

The social insurance program makes up about 20 percent of government expenditures and 4.9 percent of gross domestic product, or roughly $708 billion in 2010, according to the Center for Budget and Policy Priorities.  

Under current law, full retirement benefits kick in at age 66 for those entering the program now.
Social Security policy has gotten extra attention as President Obama's debt commission met over the course of this year to tackle spending issues, considering changes to entitlement programs among several options. Recommendations are due in December.

Those concerned about Social Security changes argue that the fund has been solvent for decades and did not contribute to the deficit. They say the $2.5 trillion surplus credited to the Social Security Trust Fund, along with the interest on that money, should render any big cuts to Social Security unnecessary even though the entitlement program is expected to pay out more than it takes in this year -- and enter the red permanently sometime around 2015. 

But others, including the Republican co-chairman of the debt commission Alan Simpson, say that because the federal government has borrowed against the trust fund's surplus for so long, all that's left are IOUs -- and to redeem them would mean more borrowing. 

Alaska Republican Senate nominee Joe Miller has gone further than Rubio or Paul in criticizing Social Security. 

In an interview with CNN in September, he touted a privatized system as "an account that the government is not going to steal from." Asked whether he'd be open to ending "federal Social Security" for Americans being born now, he said: "Absolutely." 

Nevada GOP Senate nominee Sharron Angle has tried to modify her statements about Social Security since earlier in the primary season. The Tea Party-backed candidate said earlier the program should be phased out "in favor of something privatized," but later clarified that she wants to "personalize" Social Security. 

Senate Majority Leader Harry Reid's campaign persistently has accused Angle of wanting to dismantle Social Security. Similar accusations fly in the Ohio Senate race, where Democratic Lt. Gov. Lee Fisher has claimed Republican Rob Portman is a cheerleader for privatization -- pointing to a comment Portman made several years ago in which he called former President George W. Bush's partial privatization plan "very sound."  

Portman denied supporting privatization at a debate Monday, but says the system needs to be reformed.