CHICAGO (AP) – State elections officials voted Aug. 11 to keep a same-sex marriage referendum off the November ballot, but supporters of the measure want a federal court to intervene.

The Board of Elections agreed with a hearing officer’s findings that there weren’t enough valid signatures to put on the ballot an advisory referendum asking voters if the state constitution should be amended to ban same-sex marriage.

“Unless they pull a rabbit out of a hat in federal court, it’s not going to be on the ballot,” said Patricia Logue, senior counsel for the Lambda Legal Defense and Education Fund.

A 1996 Illinois law already prohibits same-sex marriage, but opponents of same-sex marriage say they fear courts could overturn the law unless the state constitution is changed. More than 40 states have taken steps to define marriage to ban same-sex marriage either through constitutional amendments or with statutes.

Organizers of the same-sex marriage referendum are claiming in federal court that getting a referendum on the Illinois ballot is both burdensome and unconstitutional because of the complicated process to gather and verify petition signatures, said Peter LaBarbera, executive director of the conservative Illinois Family Institute and Protect Marriage Illinois.

But LaBarbera and other same-sex marriage opponents were rebuffed earlier this month when a district court judge dismissed their claim so now they want a federal appellate court to intervene.

“It’s not near over,” LaBarbera said.

Last month, elections officials said there weren’t enough valid signatures in a sample check of some of the more than 330,000-plus signatures they had to consider for the petition. The requirement is that more than 95 percent of the sample’s signatures are valid, and same-sex marriage opponents had 91 percent.

Both Democratic Gov. Rod Blagojevich and his Republican challenger, state Treasurer Judy Baar Topinka, applauded keeping the measure off the ballot, although neither supports same-sex marriage.

“Don’t tinker with the constitution if you don’t have to,” Topinka said at the State Fair in Springfield.

Blagojevich, who was also at the fair, agreed.

“I don’t support gay marriage, but I also don’t support efforts to further divide our community by trying to pass laws or change constitutions when the law is already sufficient as it is,” he said.

A June poll showed that a majority of Illinois voters said they oppose same-sex marriage but only 40 percent support asking state lawmakers for a constitutional amendment to ban it, according to the poll by the Chicago-based Glengariff Group. Fifty percent were opposed and 10 percent were undecided.

Actually amending the state constitution would be a lengthy process. The most common approach would be for both chambers of the Legislature to vote by three-fifths majority to put an amendment on the ballot, where it would then have to be approved by three-fifths of voters.