At least it is a Ponzi scheme according to Rick Perry.
Now, you might be tempted to be a wee bit skeptical of Rick Perry on this point.
That skepticism is justified.
But the mere fact that Governor Perry has problems with the reality of evolution (supported by mountains of evidence) and anthropogenic global climate change (ditto), the mere fact that he is taking positions utterly at odds with reality on other matters does not invalidate his contention that Social Security is a Ponzi scheme.
No, the only way to ascertain the truth of this claim is to look at the actual facts without any bias or preconceptions.
So let us go bravely below the fold to ascertain the truth, no matter how unpalatable.
(If the truth is that Social Security is a Ponzi scheme, then we'll have to deal with it; if the truth is that Social Security isn't a Ponzi scheme then Governor Perry....will keep on calling it one anyway.)
In a Ponzi scheme, promised returns come from new contributions. Ponzi schemes are unstable because they depend on continually increasing the number of contributors. They usually have a reasonably short life, though that can be lengthened if no actual payments are made. Further, to entice new participants and retain old ones, Ponzi schemes usually promise returns that are very high.
Immediately, one can see some differences as Social Security has made payments for decades and is expected to be able to do so for additional decades. Further, Social Security does not promise high returns.
The key difference, however, is that Social Security is funded by taxes, not voluntary contributions and that benefits are not promised returns. Thus, Social Security is not dependent on continually increasing the number of contributors. If Social Security faces a cash flow issue it can reduce benefits (without affecting contributions) or increase revenue (without promising higher revenue) or both. The Social Security system has done these things before and can do so again (unlike a Ponzi scheme, which, um, just can't).
So after careful (but not really difficult) analysis we can conclude the following:
Social Security is not a Ponzi scheme.
And, Rick Perry, should not be a serious candidate for President.