All those who think that gay rights should be handled at the state level need look no further than Ohio's proposed "Issue One" amendment to see the dangerous consequences this could bring. In Ohio a state constitutional amendment is on the ballot that would not only ban same sex marriage, but also the legal protection of ANY legal arrangements between same sex couples. This would include partnerships and civil unions. So to say that this issue should be decided at the state level is to open the door to the possiblity of widespread discrimination of the kind that not even the Republican party endorses (at least officially anyway).
From the Cleveland Plain Dealer:
A bad marriage: "The ill-con ceived ballot drive to amend Ohio's Constitution to deny legal status to any consenting adult relationships outside the traditional bond of male-female marriage is a terrible idea. "