From National Review Online, by Ramesh Ponnuru (emphasis added):

In a way, Giuliani’s nomination would cause more trouble for the pro-life cause than his election would. The pro-life cause can survive without a pro-life president: It emerged from the Clinton years stronger than it had been at their beginning. But it will find it harder to survive without a pro-life party. And that would be the meaning of his nomination, even if most Republican congressmen and governors remained pro-life, and even if the party platform, left unread and unheeded, continued to offer solidarity to the unborn. America has been a presidential nation, politically, for almost a century now. The parties are, in the public mind, their leaders; and those leaders are their presidential nominees.

The most specific polls on abortion policy ask respondents whether they think abortion should be banned altogether, banned with exceptions when the pregnancy threatens the mother’s life or resulted from rape, or allowed. Such polls consistently find that the people who want to ban abortion altogether and the people who want to ban it with rare exceptions add up to a majority of Americans. If Giuliani wins the Republican nomination, that majority will have no representation at the level of presidential politics. We will instead have a contest between a candidate who believes that taxpayers should fund abortion through the federal government and one who believes they should do it through state governments.

In 1973, the Supreme Court tried to declare an end to the state-by-state debate on abortion by setting abortion policy nationally. The New York Times, the next day, reported on the decision as a “historic resolution” of the abortion controversy. Before that day, supporters of legal abortion had claimed that their policy was necessary for women’s equality, or population control, or the promotion of liberty. On that day, however, they acquired the most powerful arrow in their quiver: the assertion that abortion policy was a settled matter, an assertion that had the strong support of the country’s journalistic, financial, and legal elites. The principal reason that the question has not been closed is that over the last 30 years the Republican party has stood — shakily at times, it is true, but always officially — against this elite consensus...

Now would be a strange moment in our politics for Republicans to abandon the pro-life cause, or even to weaken their commitment to it. The party is in serious trouble these days, for all kinds of reasons — but its pro-life position is not one of them. The public has been moving in a pro-life direction. In this season of Republican discontent, for the first time ever, a few polls show more Americans identifying themselves as pro-life than pro-choice. The 2006 elections went badly for pro-lifers: But pro-lifers, as a group, did better than Republicans, as a group. In the tightest races, the Democrats were far more likely to emphasize their economic liberalism than their social liberalism; and in a few of the tight races the Democrats won by running an out-and-out social conservative...

His nomination would, however, set back causes that most Republicans have rightly considered important, and for that very reason could weaken conservatism generally. That is reason enough to reject him.

HT: Pro Ecclesia