I voted 'no'.
In a gay marriage, all (both) people are married to each other.
In the vast majority of polygamous relationships, one man is married to multiple women--all individuals are not married to each other.
That's why I say any state-recognized polygamous/group marriage should involve the consent of all parties involved. So, if a guy has one wife, and wants another, his first wife has to approve of it first, and the new wife has to approve of the old one. That would probably keep such relationships minimal.