Jim, the PARTY must be pro-life. That is by commonly held morality ... and by the vote of the party. I think we must accept that there will be members of the party who will individually disagree, but in detail, not on the basic belief in the sanctity of life.
If they accept the direction ... and pro-life stance ... of the party, they will remain. That means we might remain strong, and have a chance to remain in power. Those who cannot accept the direction of the Republican Party on this, are of course, free to leave, as I would leave if the pro-life stance were not a key tenet of the party and a main plank of the party platform.
Their points of view on various details failing to carry, having made whatever points it is they are attempting to make, they should stay in the party, and vote for the candidate the party selects. Party cohesion demands sublimation of individual views on many issues.
For example, I will not support certain candidates in the primary. If my point of view does not carry, I will back the candidate whom the party selects, because I can be confident that on the larger issue of life and liberty the candidate, being a Republican, is pro-life. In our two-party system, there need to be "minority" members of both parties on many issues, but who fundamentally agree on the larger, basic tenets of the Party.
Giuliani, Romney, et al have been less than strong pro-lifers at various stages of their previous careers. However, based upon what they have put out so far in their campaigns, I could confidently support either one on the issue. I hope.