Mitt Romney and Barack Obama have an illustrious predecessor:
In 1790, the very first Congress—which incidentally included 20 framers—passed a law that included a mandate: namely, a requirement that ship owners buy medical insurance for their seamen. This law was then signed by another framer: President George Washington. That’s right, the father of our country had no difficulty imposing a health insurance mandate.
That’s not all. In 1792, a Congress with 17 framers passed another statute that required all able-bodied men to buy firearms. Yes, we used to have not only a right to bear arms, but a federal duty to buy them. Four framers voted against this bill, but the others did not, and it was also signed by Washington. Some tried to repeal this gun purchase mandate on the grounds it was too onerous, but only one framer voted to repeal it.
Six years later, in 1798, Congress addressed the problem that the employer mandate to buy medical insurance for seamen covered drugs and physician services but not hospital stays. And you know what this Congress, with five framers serving in it, did? It enacted a federal law requiring the seamen to buy hospital insurance for themselves. That’s right, Congress enacted an individual mandate requiring the purchase of health insurance. And this act was signed by another founder, President John Adams.
Meanwhile, a conservative law professor explains why the Obamacare mandate "passes constitutional muster" here.