Is the individual mandate constitutional?

Unlike me, Ilya Somin ia a real lawyer (in fact, I believe he's a professor of Constitutional Law). Like me, he believes that the individual mandate is unconstitutional.

In my view, the individual mandate is unconstitutional because it exceeds Congress’ powers under both the Commerce Clause and the Tax and Spending Clauses. I believe that courts should strike it down regardless of the political situation.

Frankly, I don't understand how you could possibly make the case that Congress has the power to impose the individual mandate, or much of the rest of what's in this abomination. But I'm not a lawyer...