The concept of an insurance mandate has a conservative pedigree, so its not really surprising that Rick Santorum expressed support for it at some time.
And that my friend is the dirty little secret nobody wants to know. The individual mandate was an idea that came from our side. Everybody, except Ron Paul, in the race was for an individual mandate back in the 90’s. It was their answer to Hillarycare.
Yes, I recall that the Heritage Foundation proposed a plan that included an individual mandate, as well as reforms that allowed purchases across state lines, but the insurers were still private.