Twenty years from now, polygamy will be legal in the United States. How do I know this? Because there's no longer a good argument against it. Gay marriage has made polygamy inevitable.
Here's what I wrote in a message entitled, Marriage: Is "Poly" the Next Step?, posted here on June 30, 2005:
While the proponents of same-sex marriages deny that they favor any developments beyond extension of the right to marry to same-sex couples, the "wall" that will be torn down by their efforts will no longer be effectively in place to address any other definitions that may be advanced for marriage. All of the arguments being advanced today to "change society's morality" to gain acceptance of same-sex marriages -- fairness; equality; acceptance of minority (that is, non-mainstream) points of view and practices, and so on -- can be made in favor of the "polys"; polygamy (one husband, many wives), and polyandry (one woman, many husbands). Indeed, here in the "wild, wild west," we have a group with significant money, power, and influence, whose central tenets at one time required its adherents to practice polygamy as the best way to salvation. The Church of Jesus Christ of Latter-Day Saints (known to many as the "Mormons") only rescinded this as a principle of belief when required to do so by the federal government as a condition for admitting the territory of Utah as a state. Why would they not return to this practice if the mood of the nation is to change the "traditional" understanding of marriage as the union of a man and a woman to allow same-sex marriages? After all, the proponents of polygamy have Biblical precedent on their side (at least, in the Old Testament), where many of the patriarchs had multiple wives. The practitioners of the Islamic faith also are permitted as many as four wives. Why should either of these groups refrain from entering the fray, and extend the definition of marriage to allow their religious beliefs to be practiced? Granted, part of the problem is that the practice has often been abused, with men marrying girls under the usual state-established age of consent -- girls young enough to be their daughters. But the abuse doesn't abrogate the right; and there's no reason why, with proper documentation, women of legal age to marry should be denied entry into a polygamous marriage if they choose to do so of their own will.
Nor should the legalization be limited to polygamy. After all, that would be unfair to that part of the female population who would prefer instead to have several husbands providing for their care, comfort, and pleasure. Again, as long as everyone is at or above the age of consent, and enters knowingly into such a union, registered with the state, why should anyone object? And, while there isn't (so far as I know) a "poly" for more complex relationships, there's no need to limit the establishment of some sort of "multiple marriages," where, say, three men and two women, or three men and four women (or "a" men and "b" women) desire to be joined in marriage and be recognized as each other's spouses. With everyone at the age of consent, and all open and above-board, why not? After all, we can't use Christian morality as an argument against any of the "polys"; that argument is out-of-bounds in the dialogue today. And, after all, just because only a few people, comparatively speaking, will actually want to enter into these forms of union doesn't make them wrong. Even though they are only a small minority, hey, minorities have rights, too -- remember? (See above.)
Still, it's a mixed blessing. It's nice to be vindicated by comments in the secular press. But how sad to be "right" about this particular issue...