But we've hashed this particular issue to death

It's the same issue. In fact, to my mind, there are several issues, which are all confused, whether deliberately or accidentally, by those talking about it.

1: Whether "marriage" should, as a term, be controlled by a religion (in this case, Chrisitianity) and therefore whether couples or (to extend this to polygamy) groups should be able to get "married".

There's nothing stopping a gay couple or a group of people in a polygamous relationship having some sort of ceremony to affirm their love and committment to eachother. It's just that they're not allowed to call it a "marriage".

2. Whether "life partners" should be able to get the benefits currently restricted to heterosexual married couples.

And this is where the confusion arises. Because the government calls this "marriage" and the church calls the other thing "marriage", everybody gets het up about it.

Now, moving on to polygamy: there's almost certainly no way that the church will be happy with it. Thus the only problem with the first definition is that the church reserves the word "marriage" to itself.

As far as the second definition goes, I don't see a problem with it, as long as the electorate wants it. There would need to be a proper framework put into place governing the various rights -- it's not quite so simple as with two people. When the husband dies, for example, in a monogamous relationship, there's no danger of squabbling among the wives.

Now, personally, do I have a problem with polygamy? I'm not sure.