“People are so simple, and so dominated by their present needs, that whoever wishes to deceive will always find another who wishes to be deceived.”
From The Prince, Chapter XVIII. Admittedly the translation is somewhat free; the Italian goes: “e sono tanto semplici li uomini, e tanto obediscano alle necessità presenti, che colui che inganna troverrà sempre chi si lascerà ingannare.”
So the last phrase is really something like “one who will let himself be deceived.” But in my misspent youth I saw something close to the phrasing above in a translation I can no longer find, and much prefer it to the less poetic version Machiavelli actually gave us.
In this case, Romney is promising the folks who don’t want “their money” spent on “those people” that he will save the money without actually making any actual human being – other than a public employee – actually suffer. And they want to believe him.
That’s over and above the usual con-artist’s trick of making the dupe believe that he’s in on the con: the respectable Republicans want to believe that he’ll betray the wingnut haters, and the wingnut haters are sure that he’s going to double-cross the respectable folks.