Iowa State Senator Dennis Guth, a Republican, on Tuesday filed a resolution which seeks to put an amendment in the Iowa Constitution defining marriage as a heterosexual union.

Social conservatives vowed in 2009 to undo an Iowa Supreme Court ruling legalizing marriage for gay and lesbian couples.

In 2010, lawmakers in the Republican-controlled House approved such an amendment. But the effort has been blocked in the Senate by Majority Leader Mike Gronstal, who easily won re-election in November despite a high-profile effort to defeat him.

Guth's resolution has 17 co-sponsors.

“I think the way that it was done did not allow the people any input,” Guth told the Quad City Times. “The people of Iowa need to have their voice heard.”

Before it can reach voters, the measure would need to be approved by the current Assembly and in the next one elected in 2014. That is, the earliest voters could see the question on the ballot is 2015.

Donna Red Wing, executive director of One Iowa, the state's largest gay rights advocate, said she believes most Republicans will oppose the measure.

“I've talked to a number of Republicans who really want to get past this,” she said. “We're going to celebrate four years of equality here in Iowa next month. The sky hasn't fallen. It seems like a waste of the Senate's time.”

According to a Des Moines Register poll released last year, already a majority (56%) of Iowans oppose such an amendment.