This is a great day for President Obama. The argument against Obamacare from constitutional norms has been fatally wounded to the extent of winning over persuadables. To the extent that pesuadables (especially fairly low information persuadables), feel in-their-bones that the government doesn’t have the constitutional power power to tell them to buy health insurance, the endorsement of the Supreme Court is going to allay some of their concerns. Conservatives who strongly believe it unconstitutional aren’t changing their mind, but they aren’t a swing vote. The Supreme Court endorsement of the constitutionality of the law is the best public relations news Obamacare has ever gotten.
It also damages Romney in other ways. He can no longer distinguish Romneycare from Obamacare on the grounds that one is a legitimate use of state power and the other is is an unconstitutional use of federal power. Thanks to the Supreme Court, both Romneycare and Obamacare are now constitutional schemes of coverage mandates + individual purchase mandates + guaranteed issue + community rating. Romney can try to explain why what he thinks is good for Massachusetts isn’t good for America. Not impossible, but not easy, and I would guess probably beyond Romney’s power.