A ballot question that would repeal a gay marriage law in Iowa would narrowly fail, a new poll released Sunday found.

The Des Moines Register asked 800 adults how they would vote on a proposed amendment to the Iowa Constitution that would define marriage as a heterosexual union, thereby reversing the 2009 Iowa Supreme Court ruling that brought the institution to the Midwest.

Thirty-eight percent of respondents said they would vote against the question, while 35 percent favored amending the constitution, and 27 percent said they wouldn't even vote. That's a 6 percent drop in support for the proposed amendment since an earlier poll conducted in September.

“You just have this spider web of mixed-up attitudes on this,” said J. Ann Selzer, the poll's director. “The rhetoric is so polarizing that you forget there's a middle on this and it's probably the middle that would make the difference.”

The GOP-led House approved the measure earlier this month with a 62 to 37 vote that fell mostly along party lines.

Passage in the Senate seems less likely. Senate Majority Leader Michael Gronstal, a Democrat, has vowed to keep the resolution from reaching the chamber's floor for a vote.

Before voters could decide to amend the constitution, lawmakers must approve the measure in two consecutive legislative sessions. The earliest that could happen is in 2013.

Polling in New Hampshire shows a similar repeal effort failing.