Update: Consistent? Absolutely! Step one, then step two!
My brother says "yes." I remain unconvinced.
Watch this video of the Massachusetts gubernatorial debate. Romney argues forcefully that he will not change the pro-life laws. In fact, he argues with the sort of passion that suggests he is either (a) an extremely polished liar or (b) earnestly committed to what he is saying.
If you watch this interview with Jan Mickelson, though, where Mitt doesn't know he's being videotaped, you'll see the exact same passion that he demonstrated in the gubernatorial debates. He's so passionate that he barely restrains himself, an excellent indication that he is not managing his words so they are politically appropriate. Rather, he is earnestly committed to the separation of church and state.
On this issue, at least, Mitt seems consistent. As for the others? I don't know, but it's plausible that the same explanation could be used for all of them--personally, Mitt has always held conservative opinions but has thought that his political position needs to represent the will of the people that elect him.
What is clear is that the "flip-flopping" charge is probably the single greatest hurdle Romney will have to overcome. Reminders of Kerry will doubtlessly prove rhetorically effective, even if inaccurate.
(HT: Jim for the first video)