I still don't understand who these 18% non-religious anti-gay marriage people are.
People who are defintion purists, i.e. there can't be a gay marriage by defintion. Jesse Ventura falls in this group.
People who don't care one way or the other if civil unions exists. I fall into this group. But I would vote yes at this point with the bandwagon effect.
People who think that marriage should not exist as government entity. I can't point to someone who would vote no as a result. But I personally don't think government should recognize marriage. I could see someone voting no on principle.
And in any poll, you get people who are trying to **** with the poll for kicks. Unless they pushed the respondents hard on this, that's an issue.