Like Romney, he was once pro-choice and is now pro-life.
Thompson was for Amnesty as recently as early 2007; now he's not.
All politicians flip-flop. Romney's only flaw in this regard is that he doesn't do as good a job of hiding as some others.
If you examine it objectively, McCain is the biggest flip-flopper of them all. Pro-Amnesty, now not. Against the Bush tax cuts, now for them. The list goes on and on.
It seems that on the issues he changed his position he’s become more conservative.