I think that Jason's constitutional definition of settled law doesn't quite work. The question is this--what distinguishes off-the-wall from on-the-wall opposition to something? If I call for the repeal of Social Security or the defunding of the program, people would call me a crackpot. It would not help my case if I said that my actions were based on sincere constitutional objections to Social Security. That might make me seem more crazy. Thus, constitutional opposition to the individual mandate does not do the work that Jason suggests.
The support of a major political party, though, makes a position reasonable. And this, I believe, would make the law unsettled. Now it is possible for a protest movement outside of the two parties to unsettle the law. It's just very hard to pull that off. If the GOP capitulates on the Affordable Care Act, then the chances of undoing it will be practically nil. That dream will live in la-la land with the folks who want to abolish income taxes or paper money, both of which were once positions adopted by a majority of the Supreme Court.