You won’t hear much about it in the Republican presidential race, for presidential politics is a lagging indicator of political change. However, there is a subtle change, I would argue, in the priorities and intensity of Republicans on social issues, especially for the millennial generation.

Megan McArdle wrote on the subject this week. She concludes that although gay marriage and abortion are often linked there is an important distinction:

[W]hile the harm from gay marriage is pretty nebulous, the harm from abortion is pretty obvious to everyone.

(Whether or not you think it’s important enough to ban is of course an entirely separate question . . . but I think it’s fair to say that everyone recognizes that something unpleasant happens to some sort of organism that absent the abortion, will almost certainly turn into a human being.)

Well, I’m not entirely convinced all have stopped deluding themselves that abortion is no big deal. That said, her argument about “harm” is, I think, correct. For years now Christian conservatives have argued that gay marriage is an attack on traditional marriage. Frankly, it never made a huge amount of sense that traditional marriage would be harmed by emulation, but now it is practically a laugh line. We see gays getting married. We see heterosexuals getting married. So where is the harm to straight couples? (Arguably, heterosexual domestic partnership is a much greater threat to marriage since it gives couples an excuse not to tie the knot.) Likewise, the argument that gay marriage is bad for kids (who will be poorly raised or subjected to school indoctrination) is undercut by our collective experiences in seeing children raised by gay couples and by the very active local control of schools that these same conservatives exercise. In sum, the arguments against gay marriage are increasingly weak while the experience of younger voters (and older ones too) has changed by virtue of their interaction with gay family members, colleagues and friends.

But what about abortion? Here, the argument is tilting the other way, in large part because of medical advances. We can see a child in utero. Doctors operate on these patients. An entire industry has sprung up to produce music to play for the in-utero listening audience. It’s getting hard on this one to argue that abortion does not involve destroying a life. Even those who generally favor keeping most abortions legal recoil when they read about “the killing in utero of one perfectly healthy twin ” for lifestyle reasons.

This doesn’t mean that the entire country will be pro-life in a generation. But it does explain why a significant number of millennials, who have grown up with magnificent modern technology and increasing and social tolerance, could be pro-life and pro-gay rights. And, of course, you have groups (GOProud, most dramatically) which encapsulate this phenomenon.

We aren’t going to see the GOP shift overnight, but Texas Gov. Rick Perry’s apparent conversion of convenience on the 10th Amendment and gay marriage will, I will predict, in a generation seem inexplicable. Republicans have a solid argument that social policy shouldn’t be imposed by courts, but as the population shifts its views the GOP will reflect that shift or be in the uncomfortable position of havng to oppose democratically chosen social policy. (As for an anti-gay marriage Constitutional amendment, who actually believes there would be enough states to ratify it?) This does not make opponents of gay marriage “bigots”; but I do believe they are in the processing of losing the argument and the country.