I welcome your two major corrections in case anyone is contemplating voting for Mitt, which I certainly wasn’t :-) Nevertheless — and despite almost all evidence — politicians are human too, and it would be nice to suppose that every once in a long while, they do something because it is right and not because it is political. In the instance, Mitt has a point that this change is anything but politically popular, so you have to wonder if he didn’t switch for good reasons.
That depends on what you are running for. In Mitt's case, to get the GOP presidential nomination, it is an absolute must.