So it's clear the tack that the right is going to take after the constitutionality of Obamacare is upheld: "It's a tax! OMG Obama raised taxes on everyone!"
The retort to that is easy. Obama taxed America for health care? Then Romney taxed Massachusetts! How does the GOP support a guy who does such a thing?
Mitt Romney had a tiny bit of wiggle room that he could use to pretend that it was OK to implement Romneycare in Massachusetts, but that Obamacare was unconstitutional. He claimed healthcare was a states' rights issue, and that each state was free to do what it wanted but the federal government was out of its jurisdiction to implement a national plan that was just like his plan.
But now, the SCOTUS has said that argument is totally bunk. Instead, they have labelled Obamacare as a tax. And FOX News and the like have jumped all over this - the chyron on FOX News after the decision was "Supreme Court upholds Obamacare as a tax". Conservative talking heads have been repeating "tax tax tax taxity tax tax" until they're blue in the face.
Except there's one problem here - Mitt Romney imposed this EXACT same "tax" on the people of Massachusetts. Not only that, but he pioneered the use of such a tax! And the wiggle room is gone - there's no coherent way to say "a state tax for health care is OK but a federal tax is unacceptable!"
So this should be a slam dunk. If it's a tax, Romney embraced this tax with open arms, and he's your nominee. You have to own that now. Good luck with that.