Difference is within poll's margin of error.

Minnesotans are about evenly divided over a constitutional amendment to ban same-sex marriage, according to a Star Tribune Minnesota Poll published Sunday.

Six weeks before Election Day, 49 percent of the likely voters polled supported the proposed amendment, while 47 percent opposed it, the newspaper reported (http://bit.ly/Uq6TVB ). The two-point difference is within the poll's margin of error of plus or minus 3.5 percentage points. Four percent of those polled said they were undecided.

The poll also found that Minnesotans tend to favor a constitutional change that would require voters to show government-issued photo IDs before casting ballots, but support for the idea has declined over the past year, the newspaper reported (http://bit.ly/QsMTU3 ). Slightly more than half of likely voters polled — 52 percent — supported the photo ID amendment while 44 percent opposed it and 4 percent were undecided.

Support for a photo ID requirement is down from the 80 percent reported in a May 2011 poll, when the issue was debated as a change in state law rather than as a constitutional amendment.

The poll, conducted by Mason-Dixon Polling and Research Inc., surveyed 800 likely voters by phone Sept. 17-19.

Minnesota law requires that any constitutional amendment must win approval from a majority of all ballots cast. A voter who skips the question is counted as a no vote.

The poll found overwhelming support, though, for civil unions that would offer gay and lesbian couples the same legal rights as marriage. Overall, 68 percent of respondents would support civil unions, only 23 percent would oppose them.

Groups on both sides said they were encouraged.

Frank Schubert of Minnesota for Marriage said it shows "we are in good shape and reinforces our belief that if we execute our game plan, we will pass the amendment," said.

But amendment opponents said the poll shows they can defeat it.

"It's clearly an incredibly close race and will be a dead heat down to Election Day," said Richard Carlbom, campaign manager for Minnesotans United for All Families.

Supporters of photo ID say it will prevent vote fraud. Opponents say there is no evidence of significant fraud and fear it will disenfranchise some poor, elderly and student voters who are less likely to have ID cards. They say it is part of a national attempt to suppress Democratic votes.

Rep. Mary Kiffmeyer, R-Big Lake, sponsor of the photo ID amendment, said she's pleased it's still "strongly supported," despite what she called opponents' mischaracterization of its effects. She said same-day registration, absentee and mail-in voting would continue, contrary to claims they would end or be limited.

"The negative misinformation may have an effect," she said. "But it still shows photo ID, even with all that, winning strongly."

Photo ID foe Rep. Ryan Winkler, D-Golden Valley, said it is "exciting and surprising" to see support dropping for the idea.

"I think voters are smart," he said. "They don't always know all the facts. When they start to learn all the facts, they're very good at making a good judgment," he said.