It was a close-to-impossible assignment: explain why the Massachusetts health care reform was good policy and President Obama's health care reform, so strikingly similar, wasn't. In his speech at Ann Arbor last week, Romney did advance the only principled defence of this position--which is that states can properly do things that the federal government cannot. Let the states experiment; don't impose one top-down solution. Moreover, you can argue, the Constitution denies the federal government power to make people buy health insurance; nobody, so far as I know, denies that this power is available to the states.
This federalist approach, as Romney called it, is a defensible position, and probably even correct as far as it goes, but it is plainly no use politically. Republicans do not want to hear key pieces of the Obama reform--the individual mandate, the exchanges, and so on--defended on their merits as attractive options for (some) states, or to be told that problems only arise when the feds get involved. They want to hear the policy repudiated in every possible way. They want to hear that the Massachusetts reform has failed.
Romney gave an engaging speech (as usual) and it was probably as effective as it could be. Had he disowned his own reform it would have been another insincere flip-flop, and that would have attracted even more criticism. He chose not to, and defended his reform pretty well. Even so, there were elements of trying to have it both ways. His discussion of differences between his reform and Obama's policy concentrated on inessentials, as it had to; the similarities are so much more important. He protested too much.
Also, an unresolved tension in his position became obtrusive. He advocates (a) state by state solutions, according to their very different needs and preferences (query: are they so different?) and (b) improved portability of insurance coverage from job to job, or from job to no job, as the case may be. That doesn't work. If portability is important--and it is--this argues for a national solution, or at least for state solutions that conform to a national template. The more you emphasize portability, the harder it is to denounce federal involvement.
Ross Douthat argues that Romney should just have disowned the individual mandate; this would have threaded the needle, he argues. Yes, he could have done that. But you have to have the mandate (or a constitutionally permissible substitute) or else the plan fails, and for exactly the reasons Romney adduced in his speech. Ross also calls Romney's federalist position--that his plan is good, but states should be able to choose their own way--"horribly incoherent". Actually, despite the portability point, it is reasonably coherent. The problem is, it is bad politics, and if you are running for office that is what counts.
I cannot see how Romney gets past this issue. It's a shame. He is in many ways a capable and attractive candidate. And he is far more popular with the Republican electorate than you would expect, given that he is, in effect, an old-fashioned moderate. On health care, you could call him a conservative Democrat. US politics could do with more like him. It is tribute to his charm and tenacity that the GOP, intent on purging all RINOs, has not definitively spat him out already. But surely this is only a matter of time.