The money quote from the section on the mandate: Our precedent demonstrates that Congress had the power to impose the exaction in Section 5000A under the taxing power, and that Section 5000A need not be read to do more than impose a tax. This is sufficient to sustain it.
My sense ...
On John Roberts' part, this is vaguely similar to Chief Justice John Marshall's ruling in Marbury v. Madison, which, in laying down the legal concept of judicial review, indeed found irregularities in the executive's argument. But since the underlying cause before the Court--created by Congress--was itself flawed, the executive's argument in effect prevailed. In sum, Marshall found a way to hold for a president he detested (Jefferson) while asserting his own independence and affirming his own authority.
Marshall's ruling was brilliant then, and Roberts' is almost equally so.
One also profoundly suspects that Roberts saw an opportunity to stem the inescapable rage the Court faced otherwise; and in this sense Roberts was as political as judicial, but for once it was a prudent--and in that sense acutely conservative--kind of politics.
With Roberts having joined the Sane Gang of Four, we may have just turned a long and agonizing corner.