Minnesotans favor a constitutional change that would require voters to show government-issued photo ID before casting ballots, but their support has weakened dramatically over the past year, the Star Tribune Minnesota Poll has found.

Slightly more than half of likely voters polled -- 52 percent -- want the changes built around a photo ID requirement, while 44 percent oppose them and 4 percent are undecided.

That is a far cry from the 80 percent support for photo ID in a May 2011 Minnesota Poll, when the issue was debated as a change in state law. Support among Democrats has cratered during a year marked by court battles, all-night legislative debates and charges that the GOP is attempting to suppress Democratic votes.

Republicans and independents continue to strongly back the proposal, which passed the Legislature this year without a single DFL vote.

But 52 percent approval is a thin margin for a constitutional amendment six weeks before the election. A change in the Constitution must secure a majority of "yes" votes from all ballots cast. That means a voter who doesn't vote on the issue in effect votes no, setting a higher bar for passage.

Paula Rude of Robbinsdale supports photo ID. "Currently they don't ask anything," she said. "You state your name, sign a book and go vote, unless you're not currently registered." She added, "My position is, people know when the vote is coming, and they ought to be prepared."

Joseph Valerio of New Hope works as an election judge, opposes photo ID and says he has not seen any apparent fraud. "It's a stupid solution to a nonexistent problem," he said. "The other side has not produced a damn iota of proof that any kind of fraud exists."

Rep. Mary Kiffmeyer, R-Big Lake, sponsor of the photo ID amendment, said she is pleased that it is 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 that they would end or be quite limited.

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

On the other side, Rep. Ryan Winkler, DFL-Golden Valley, a photo ID foe, said it is "exciting and surprising" to see support dropping for the amendment.

"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."

The proposal would require all in-person voters to show a government-issued photo ID. It also would set up a new, two-step system of provisional balloting for those without the ID and end "vouching" for those who register without proper ID on Election Day. Opponents say the plan may affect some aspects of same-day registration and absentee voting.

Amendment supporters say the changes are needed to prevent fraud. Opponents say there is no evidence of significant fraud. They fear the amendment will disenfranchise some poor, elderly and student voters and say it is part of a national attempt to suppress Democratic votes.

Last year, the Minnesota Poll asked if respondents would "favor or oppose requiring Minnesota voters to show a photo ID in order to vote." Nearly two-thirds of Democrats and 83 percent of independents said yes then.

Dayton vetoed the 2011 bill. Kiffmeyer, a former secretary of state, proposed the idea this year as an amendment, which goes directly from the Legislature to voters.

Opposition has hardened since then from the DFL, the League of Women Voters, AARP and organized labor. Court challenges have emphasized the complexity of the changes beyond the ID requirement.

In the new Star Tribune Minnesota Poll, 800 likely voters were asked how they would respond to the ballot question: "Shall the Minnesota Constitution be amended to require all voters to present valid photo identification to vote and to require the state to provide free identification to eligible voters, effective July 1, 2013?"

Democrats have turned against the idea -- only 22 percent of the likely Democratic voters support it in the Minnesota Poll. Independents, who favored photo ID by 83 percent in 2011, now support it by 61 percent. Republican support remains strong at 87 percent. The poll, conducted Sept. 17-19, has a margin of error of plus or minus 3.5 percentage points and included land lines and cellphones.

Support for photo ID is strongest in the metro suburbs, weakest in the Twin Cities and Duluth. Men are more likely to support it than women. Those making less than $50,000 strongly oppose it while those making above that favor it.

Jon Burnison of Hamel supports the change to prevent fraud. "It doesn't seem that it would be that much of a hindrance for the average voter," he said.

Dorothy Erholtz of Grand Rapids doesn't think the requirement is needed. "A lot of older people wouldn't have that ID," she said.

Jim Ragsdale • 651-925-5042