I think Julian Sanchez is on the same page as I am, while being less sympathetic to the individual mandate:

It does seem like a surprising result, given the last century of Commerce Clause precedent, that anything plausibly describable as economic activity might be found beyond the power of Congress to micromanage. “Preposterous on its face,” even.

But isn’t it preposterous that it’s preposterous? Step back from that steady accretion of precedents and instead just ask how far a federal power to “regulate commerce…among the several states”—especially in the context of separate and parallel powers to regulate commerce with foreign nations and Indian tribes—can plausibly be stretched. Isn’t it the idea that “regulate commerce” could entail a power to require a private individual in a single state to buy health insurance that ought to seem kind of crazy? Shouldn’t we find it more intuitively preposterous that a provision designed for tariffs and shipping rules should be the thin end of the wedge for a national health care policy?

This is what I mean when I said that if the ruling was based on prior legal precedent, constitutionality wouldn’t be a problem. What bothers me is I still have yet to hear a good liberal response to the argument that the interpretation of the Commerce Clause that says you can tax people for not buying health insurance could apply to basically anything Congress wanted to apply it to. Doesn’t not buying homes affect the housing market? Not eating vegetables? Ect.

What liberals generally say in response is what Eric Holder and Kathleen Sebelius wrote yesterday, which is that the health care market is unique because we all get sick and so we’ll all eventually need health care, and people’s decision not to purchase it makes it impossible to control costs, making the mandate necessary. But whether or not the mandate is necessary for the law to work is actually a separate question from whether or not interpreting the Commerce Clause this way means the federal government, at least in the abstract, can basically do anything it wants. That’s the argument that makes the mandate unpopular, whether or not it should be overturned based on what the court has said in the past. So I think politically at least, liberals really need to think harder about how to respond to the conservative critique of the mandate, even if it is cynical and opportunist. Just saying “precedent says x” isn’t really enough.