Actually, I'm not sure that that would tell us if
Romney is "really" a pro-lifer. Politicians have to pick their
battles, after all, and given the political climate in
Massachusetts, he might well have chosen to keep his pro-life
sentiments to himself, given that they'd not only be politically
damaging but would make no difference in terms of policy.
Another possibility is that the change of heart preceeded the
choice not to seek another term, since running in Massachusetts
would have required him to maintain a publicly pro-choice stance,
and he couldn't stomach the disingenuous that that would require.
If that's the case, than the question is totally inapposite: He
only would have chosen to run for a second term if there had been
no conversion.
In any case, we should be less concerned with what a politician
believes in his heart than in what he'd do in the real world. On
that score, my sense is that a President Romney would indeed be
allied with pro-lifers most of the time.