Which is more likely?

[tpfkaw]

I'd say the former - Giuliani was seriously talked about in '08, and led in the polls several times (although he ran a terrible campaign), while Pataki (and Giuliani) is being semi-seriously talked about for 2012, and Colin Powell could easily have had the nomination had he ran in 1996, while Forbes ran a serious pro-choice campaign that year.  I can't recall the last time a pro-life candidate was seriously talked about for the Democratic nomination.

[DrScholl]

The Republicans nominating a pro-choice candidate, they might have a hard time with some conservatives, but they could still squeeze through. A Pro-life Democrat wouldn't get through many primaries, at least not the big ones.

[FEMA Camp Administrator]

sadly, the first one.

[Yelnoc]

The Republicans are an evangelical-libertarian coalition with an emphasis on the first component; they would never nominate a pro-choice candidate.  The Democrats are the "not Republicans" party and thus a bigger tent with more diverse views, making it easier for a democratic pro-life candidate to get through the primaries.

[dmmidmi]

As time goes on, I don't think that either is really outside the realm of possibility. To be sure, abortion will likely always be a divisive wedge issue. That being said, I could see a future where Republicans stress fiscal conservatism as the central issue of their platform--not necessarily forsaking social conservatism, but framing a platform as such that abortion, gay marriage, etc. are secondary to economic issues.

For example, in the state in which I live, I think Rick Snyder sort of embodied that sort of message. He had indicated that he was pro-life in interviews and the like, but that wasn't the central argument of his campaign, and he could have won just as easily had he been as pro-choice as your average run-of-the-mill Democrat. I simply don't see a pro-choice Democrat making it through a Presidential primary without a drastic shift to the right in terms of the overall mentality of the electorate.

[RIP Robert H Bork]

The former, very unfortunately.

[Dgov]

Pro-life Democrats would be far more likely, given that the party is increasingly composed of generally Pro-life Minorities.  A Pro-life Hispanic Democrat could probably win the Democratic primary, especially if he/she is a solid Liberal in other areas.  Is there any Democrat on this forum for whom abortion is a completely make/break issue?