According to this blog post by Robert I. Field in today's Philadelphia Inquirer, great minds at the conservative think tank the Heritage Foundation created the idea of mandated health insurance coverage back in 1990.
Apparently, the Heritage Foundation isn't exactly shouting this from the rooftops. But their report, "Using Tax Credits to Create an Affordable National Health System" [a pdf file], states that "...government would require, by law, every head of household to acquire at least a basic health plan for his or her family. Thus there would be mandated coverage under the Heritage proposal ..."
Check it out -- top of page 7. Along with Field, I wish we could get away from partisan bickering, and return to "reasoned public discussions."