Here's the definition of a Ponzi scheme.
A Ponzi scheme is an investment fraud that involves the payment of purported returns to existing investors from funds contributed by new investors.Here's how social security works.
The Social Security system is funded primarily by federal taxation of payrolls.
Doubtless PolitiFact might defend itself by noting that "fraud" occurs in Chartier's definition of "Ponzi scheme." The PolitiFact argument insists against the evidence that Ponzi schemes require fraud in order to fit the proper definition.
But that's only true if we cherry-pick the definition.
Chartier's criticism hits its mark, but would have more force if she pointed out that fraud is not a necessary feature of Ponzi schemes and Ponzi financing.