I'm guessing polygamy is next. Much more support for it.
Yes, there is some ancient precedent for polygamy in the Judeo-Christian tradition, although it died out within Judaism long before the time of Christ.
By contrast, there is zero support for buggery. I find it amusing that the same liberals who want gay marriage claim to find polygamy abhorrent.
Most of our population (and probably nearly all of the liberal population) lives in serial polygamy already. Their support of the one and their rejection of the other has absolutely no basis in logic...