Back in April, Jonathan Rauch took on the subject of federalism and "hot button" social issues and also came to the Giuliani/Brownstein view that federalism makes these debates less contentious. Rather than argue a priori, Rauch contrasts the debate over abortion with the debate over gay marriage:

The result is a diversity of practice that mirrors the diversity of opinion. And gay marriage, not incidentally, is moving out of the realm of protest politics and into the realm of normal politics; in the 2006 elections, the issue was distinctly less inflammatory than two years earlier. It is also moving out of the courts. According to Carrie Evans, the state legislative director of the Human Rights Campaign (a gay-rights organization), most gay-marriage litigation has already passed through the judicial pipeline; only four states have cases under way, and few other plausible venues remain. “It’s all going to shift to the state legislatures,” she says. “The state and national groups will have to go there."

For one thing, Rauch's trend data here isn't particularly solid. Yes, gay marriage played less of a role in 2006 than it did in 2004, but that trend may not continue. The abortion debate has continued to be contentious for decades, but it has ebbed and flowed somewhat. But more to the point, insofar as Rauch is correctly identifying the dynamics of the issue here, I think there's a more plausible explanation -- the main arguments against gay marriage are actually factually disproven by increasing acceptance of gay partnerships. The dawn of gay marriage in Massachusetts and of civil unions in Vermont has not, in fact, led to the collapse of heterosexual marriage throughout New England.

The legalization of abortion, by contrast, actually has been associated with an increase in the number of abortions. If you believe that abortion is a serious moral wrong, there's nothing about seeing some jurisdictions legalize abortion that would make one rethink that. If, by contrast, you think that legal recognition of gay partnerships spells big trouble for family life, then looking at places where some of it exists will dispel those worries. One should also note that opposition to gay equality measures is highly generational in nature and is pretty clearly grounded in irrational prejudice rather than deeply felt philosophical disagreement.