A new poll indicates that Minnesota voters are turning against a proposed constitutional amendment to ban same-sex marriage.

Public Policy Polling's newest sampling indicates that 49 percent of voters oppose the measure, while 43 percent support it.

That's a shift from four months ago, when 48 percent supported the amendment and 44 percent rejected it. That was still shy of the 50 percent needed to pass a constitutional amendment.

Public Policy surveyed 973 Minnesota voters from May 31 to June 3 and placed the poll's margin of error at 3.1 percentage points, plus or minus.

"Today's poll shows there is a conversation happening across this state about what marriage means and how this amendment would limit the freedom to marry for gay and lesbian couples," according to a statement from Minnesotans United for All Families, the lead group opposed to the amendment. "The more people talk about this, the more likely they are to vote no in November, and this poll demonstrates that more and more Minnesotans are coming to the conclusion that this is not the right thing to do for our state."

Chuck Darrell, spokesman for Minnesota for Marriage, challenged the accuracy of those results. "We've been polling the amendment for over a year," he said, "and our most recent poll has the race unchanged with support for the amendment in the mid-50s."

Darrell cited a tweet from the group in May, saying it does not "believe polls showing support for gay marriage" because "any time there is a vote, it doesn't back it up."

Activists on both sides of the issue have doubted the accuracy of polls on what can be an emotional and conflicting issue.

In Maine, where a similar measure was on the ballot in 2009, polls consistently showed it being soundly defeated. On Election Day, it passed 53 percent to 47 percent.

It was unclear whether voters lied to pollsters, had a change of heart when voting or some other political wind took hold of the electorate.

Public Policy Polling said the shift largely occurred among independent voters, who had strongly favored the amendment 50 percent to 40 percent, but now oppose it 54 percent to 37 percent.

The poll discovered the same sizable generational gap on the issue as in other states.

Voters over the age of 45 support the amendment 50 percent to 42 percent. Voters under 45 oppose it by 60 percent to 34 percent.

A Republican-led constitutional amendment to require photo ID at the voting booth has the support of 58 percent to 34 percent, the poll found.

The poll also put Gov. Mark Dayton's approval rating at 49 percent with 36 percent disapproving. The Legislature has a 21 percent approval rating.

Baird Helgeson • 651-925-5044