A poll giving a slender lead to opponents of the proposed amendment to the Minnesota Constitution banning same-sex marriage was released Thursday by a team of faculty members and students from St. Cloud State University.

Fifty-one percent of likely voters plan to vote against the proposal to insert a same-sex marriage ban into the constitution, while 44 percent support it.

A rarity in this election cycle, it was conducted independently and using traditional, time- and labor-intensive methods.

The poll also found eroding support for the other question on this year’s ballot, the proposed voting amendment. Thirty-nine percent would reject the measure and 55 percent of likely voters plan to vote for it.

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Undecided voters and those who said they would skip voting on the ballot questions — effectively a “no” vote in Minnesota — would not tip the balance, according to the survey of 600 Minnesota adults conducted Oct. 15-21. The margin of error is 5 points.

The SCSU effort is the first since the barrage of 11th-hour TV and radio ads, which often move polling needles, began airing.

The numbers jibe with those produced by other recent polls, which have found the voting amendment still far ahead but with eroding support and the gay-marriage ban trailing slightly.

But unlike many of the voter surveys sparking headlines recently, this one used gold-standard methodologies and appears to be quirk-free. Indeed, its principal investigators, political science professors Steve Wagner and Stephen Frank, have released a 25-page document [PDF] describing — in excruciating detail — how the numbers were obtained.

The important bits: The survey used a sample that was balanced on multiple levels. Forty percent of the numbers were for cell phones, the same percentage as Minnesota households without landlines. Live interviewers — trained students working under close supervision — alternately asked to speak with men and women and the oldest and youngest adult in the households that were called.

Voting amendment All respondents Likely voters Vote for 52% 55% Vote against 36% 39% Not vote 8% 3% Don’t know 4% 3% Source: St. Cloud State Statewide Survey Fall 2012

Respondents were asked not just their political identification and how likely they are to vote, two key elements in a poll, but a series of questions designed to ferret out actual likelihood and leaning. Also asked were questions about age, education, household income, county of residence, gender and religion.

Many surveys circulating in recent months have had local and national public opinion geeks scratching their heads because the crosstabs, the data subsets pollsters use to gauge a poll’s credibility, haven’t added up. Some have shown young voters, who typically support same-sex marriage in large numbers, voting in favor of the ban, for example, while others have confounded expectations regarding gender and rural vs. urban residence.

Marriage amendment All respondents Likely voters Vote for 41% 44% Vote against 49% 51% Not vote 7% 3% Don’t know 3% 2% Source: St. Cloud State Statewide Survey Fall 2012

MinnPost’s David Brauer and I have both written critical stories about the discordant surveys, so before pronouncing this one a to be solid and independent, I contacted longtime local polling guru Rob Daves, who teaches survey research and the University of Minnesota’s Humphrey Institute and is the principal of Daves & Associates.

As a neutral pollster himself, Daves declined to venture an opinion about the numbers themselves but cheerfully parsed the pages of fine print concerning methodology.

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“I’m glad to see a respected university poll using both cell phones and landlines in their research, compared with some of the potentially less accurate methodologies we’ve seen in the Minnesota media in the past week or two,” he said. “Support could change dramatically in the next two weeks because of the barrage of media ads and news that will center around the two amendments.”

So does this mean we can call the ballot questions and turn our collective attention to post-election topics? Hardly.

Two more items of interest regarding the SCSU poll: Regarding the marriage amendment, the numbers are almost exactly what they were when the scholars asked voters the same question one year ago yesterday.

“The overall results showed that 44 percent of respondents believed that the Minnesota constitution should be amended and 47 percent believed that it should not be amended,” they reported, while “9 percent of respondents either refused to answer or said that they were not sure.”

Other polls have shown the proposed marriage ban starting out with a majority but losing support steadily in recent months.

Lastly, this year’s survey team also asked voters whether they were confused by the wording of the proposed amendments. Critics have asserted that the language describing the voting amendment in particular is unclear.

Regarding each of the amendments, a third of respondents told the SCSU team they found the questions confusing. What does that say about the validity of their answers about how they’re going to vote? Stay tuned.