CEDAR RAPIDS, Iowa - Automated phone calls made to voters in Iowa senate 18 less than 24 hours before Election Day have both major party candidates crying foul.

Voters in the Linn County district report receiving robo-calls encouraging voters to ask Democrat Liz Mathis’ support of an Iowa Supreme Court ruling allowing same-sex marriage.

Mathis and her Republican opponent, Cindy Golding, both deny any connection to the calls a group identified as Citizens for Honesty and Sound Marriage.

The group has not filed a statement of organization with the Iowa Ethics and Campaign Disclosure Board, according the state agency’s staff. Iowa law requires groups making independent expenditures on behalf of a candidate to file within 48 hours of spending $750, according to Melody Feldt of the ethics agency. However, the way Iowa law is written makes it hard for the ethics board to know such groups exist or exceed the expenditure limit until it hears from the public.

Feldt said similar activity is not frequent, but is reported in nearly every election cycle.

“It’ picks up around election time,” she said.

When the ethics board hears about independent expenditures by groups that have not filed statements of organization it tries to reach out to them.

“We try to find out who it is and make contact to make sure they understand the code and rules for compliance, Feldt said.

In this case, her research has so far produced no results.

In Senate 18, the campaigns and their allies all deny involvement in the robo-calls. According to various people who have received calls from Citizens for Honesty and Sound Marriage, the calls says: “Did you know Liz Mathis endorses gay marriage and if she endorses gay marriage she must endorse gay sex. Call Liz Mathis… and ask her which gay sex acts she endorses.”

Mathis called it “so disappointing that my opponents have launched a last-minute, anonymous attack that is hurtful and false.”

However, her opponents were quick to distance themselves from the calls.

“It’s a distraction, it’s disturbing and disgusting,” said Golding spokesman Don McDowell. “Neither the Golding campaign or the Republican Party have anything to do with the calls and don’t endorse anything in it.”

The National Organization for Marriage, which has spent about $40,000 on behalf of Golding, who supports allowing Iowans to vote on whether to ban same-sex marriage, also denied any involvement.

NOM and The Family Leader called on the Iowa Attorney General to investigate the calls, which they labeled a “dirty trick” being played on Golding and supporters of traditional marriage.

“Yesterday a phony group claiming to support marriage launched robo- calls that were so offensive they clearly were designed to turn voters away from Cindy Golding because she supports marriage between one man and one woman,” said Brian Brown, NOM president.

Bob Vander Plaats of The Family Leader said his group has been very public about its support of Golding because she supports a referendum on a constitutional ban on same-sex marriage.

“Our involvement in the race is well known and well documented,” he said. “We would never use some phony group to deliver messages that are not only vile, they are bound to backfire.”

“Of course we had nothing to do with that and the thought that we would is absurd on its face,” he said.