Perhaps some of it reflects the zeal of converts. One side effect of the veneration of the Constitution in our political culture is that it makes people think that policies they consider unjust must be incompatible with it. Rights cannot be put up for a vote, as people often say when they are putting them up to a vote of nine justices. There may, however, be a deeper reason that the debate over same-sex marriage has taken the form it has, a reason having to do with modern constitutional jurisprudence.
The case that governments at all levels must recognize same-sex marriage under the Constitution is a pretty simple one even if it did not occur to almost anyone before the past 15 years or so: The 14th Amendment requires all states to extend the equal protection of the laws to all persons, and that means that couples wishing to get married must be treated without regard to their sexual composition.
There are three possible counterarguments, none of them incompatible with the others. The first is that the amendment’s equal-protection language does not mean — that is, was not intended by the states that ratified it to mean — equitable treatment. It means, instead, that state governments must protect citizens from theft, murder, rape, and other crimes without regard, for historically pertinent example, to their race. That’s certainly a plausible interpretation of the words. (I will discard as implausible a suggestion some conservatives have made, that the amendment bars only racial discrimination because its ratifiers had only that type of discrimination in mind, even though the text they ratified made no such qualification. On that theory a state could decide to exclude gays, or women, or redheads from police protection without running afoul of the 14th Amendment.)
The second counterargument would refer to the closing section of the amendment, which grants Congress the power to enforce the preceding parts. It would then, perhaps, note that at the time of ratification there was no expectation that judicial review would play anything like as large a role in our political life as it does now, and that it is unlikely that the ratifiers would have greeted the end of a civil war caused in no small part by judicial overreaching by giving the Supreme Court vastly greater power. It would conclude that it is largely up to Congress, not the Court, to decide what equal protection means in practice.
Either of these arguments would limit the Court’s discretion significantly — but the adoption of either would also mark a radical break with its jurisprudence. The Court has for decades assumed that it is in the business of deciding what forms of unequal treatment by governments are justifiable.
That leaves only one counterargument available: that the definition of marriage as the union of a man and a woman is not unjust discrimination against anyone. To make that argument requires explaining what traditionalists think marriage is and why same-sex couples, along with those in many other possible relationships, cannot be married — if not to persuade the justices that those views are right, at least to make them consider those views reasonable. The constitutional argument for allowing states to keep the traditional definition of marriage, in other words, is almost identical to the policy case for their acting on that freedom.
I say “almost” because it is possible to reject the traditional definition without thinking it grossly unjust. The gathering political and cultural force behind same-sex marriage has, however, been directed as much against the view that traditional marriage is reasonable as against the view that it is right. Proponents of same-sex marriage generally say that the opposition is bigoted, not just mistaken. The argument against constitutionalizing same-sex marriage that is actually being made in front of the Court occupies a shrinking cultural space.
Politicians who believe, or at least say, that marriage is the union of a man and a woman have generally not offered any reasons for their position, instead resting their case on tradition, religion, or majority opinion. Once majority opinion turned, these politicians were free to switch positions without ever having to abandon any of their arguments, since they had not made any. Traditions change, after all. The reticence of the politicians has encouraged the belief that the old view of marriage had no rational basis, and thus made it more vulnerable to modern equal-protection jurisprudence. (When the justices heard the same-sex-marriage cases, liberal commentators pronounced it “strange” that conservatives were just now arguing that marriage had something to do with procreative sex — as though this were a view that they had devised for the occasion.)
Hence Senator Portman stands almost entirely alone. And his own position may not be stable. He does not say in his op-ed that the Constitution, read correctly, allows states to decide whether or not to recognize same-sex marriage. “An expansive court ruling would run the risk of deepening divisions rather than resolving them” is all he says. He could at any point sincerely change that contingent judgment without altering any view of constitutional principle. At that time, the club would shrink to almost zero.