Washington ? A growing divide over Social Security splits the two leading contenders for the Republican presidential nomination, and the differences between Texas Gov. Rick Perry and former Massachusetts Gov. Mitt Romney foreshadow a tricky political dance with older voters.

Romney has seized on what he perceives as Perry’s vulnerability on a program that seniors hold dear, Democrats venerate as sacrosanct and Perry has labeled a “Ponzi scheme.”

That sets up a battle for older voters in Iowa, retirees in Florida and the Sun Belt, and Baby Boomers everywhere worried about their own recession-scarred retirement plans.

“If we nominate someone who the Democrats could correctly characterize as being against Social Security, we would be obliterated as a party,” Romney said on Sean Hannity’s radio program Thursday.

Perry is unyielding.

At a Friday fundraiser in California, Perry stood by his criticism of Social Security and his position that the program is best left to states to administer — a non-starter for many, including some Republicans.

“For people who are on Social Security now, like my folks, and people who are approaching Social Security, like me, it’s going to be there,” he said.

But, he said, he didn’t know at what point age-eligibility will have to be raised because the funds simply aren’t there.

“Anybody that’s for the status quo with Social Security today is involved with a monstrous lie to our kids, and it’s not right,” he said earlier this week during a debate.

An aging population has put a heavy burden on the Social Security Trust Fund: too few workers are paying for the benefits of a growing number of retirees. In 1950, there were 16 workers paying into the fund for each recipient. Last year, that ratio fell to three workers for every recipient. Left unaddressed, cuts in benefits would be forced in 2037.

But any talk of cutting benefits comes with political risk.

“Governor Perry’s immediate challenge is to knock down the hanging perception being driven that he wants to get rid of Social Security,” said Rich Killion, a Republican strategist who worked on Romney’s 2008 presidential bid and advised former Minnesota Gov. Tim Pawlenty’s bid this year.

The Romney-Perry spat comes as the contest for the Republican nomination begins to flare. With three formal debates and a handful of forums this month, the campaign to challenge President Barack Obama has taken on urgency as voters return from their summer vacations and start to pay attention to politics.

Since Perry joined the race last month, Romney has seen his lead fade, driving him to focus his aggressive criticism on Perry instead of looking ahead to a general campaign against Obama.

“The governor says look, states ought to be able to opt out of Social Security. Our nominee has to be someone who isn’t committed to abolishing Social Security, but who is committed to saving Social Security,” Romney said, sharing the stage with his rival.

An AP-GfK poll in May found that 70 percent of Americans consider Social Security deeply important to their financial security in retirement. Just 6 percent said it was “not at all” important.

Yet the public is split on the likelihood Social Security will be there for them: 35 percent say it is extremely or very likely to provide income their entire retirement, 30 percent somewhat likely and 35 percent not too or not at all likely.

It’s that uncertainty that both campaigns hope to tap.

“I know Florida certainly has an interest in Social Security given the large number of seniors we have here,” said John Thrasher, a Republican state senator and former state GOP chairman who backs Romney.

“It’s not whether it’s a Ponzi scheme or not. These are retired people who are pretty intelligent. They want Social Security to be maintained. And they understand there are problems that need to be fixed. There is an opportunity to fix Social Security so it’s a continued benefit for people who are getting it now and those who will get it in the future.”