Two vocal and high-profile Republicans traded barbs Tuesday on the contentious plan to require a photo ID for Minnesota voters, raising the dueling specters of widespread fraud and runaway expenses.

"To think that liars and cheaters and stealers exist all around us, but only angels come to vote, is naive," warned state Rep. Kiffmeyer, R-Big Lake, a former secretary of state and sponsor of the proposed constitutional amendment that will appear on the Nov. 6 ballot.

The plan, which would only allow voters with a government-issued photo ID to cast a ballot, "will add integrity to our election system. It will be easy to vote ... but harder to cheat," she told a forum in Maplewood.

But former Gov. Arne Carlson was having none of it.

Contending that Minnesota had a national reputation for clean elections, he denigrated the amendment as "a voter-impersonation law when we have no voter impersonation. ... We're giving the patient medicine for an illness they do not have."

He also cited a survey of local auditors he said put the total costs of the ID plan as high as $100 million, although Kiffmeyer countered that the potential costs would be limited to providing free IDs to those who need them, a fraction of Carlson's estimate.

The sharp exchange mirrored public debate on the plan, which is one of the year's most hotly contested ballot items. A Star Tribune Minnesota Poll taken in May 2011 showed 80 percent support for the concept. But a poll taken last month showed support had declined to 52 percent, with 44 percent in opposition and 4 percent undecided.

Tuesday's forum, sponsored by the human rights commissions of the cities of Maplewood and Roseville, drew about 100 people. Also on the panel were Carolyn Jackson of the ACLU, which opposes photo ID, and Dan McGrath of Minnesota Majority, which supports it.

McGrath, who has burrowed into state databases in search of fraud, noted more than 200 convictions for illegal voting in 2008 by felons who had not completed the terms of their probation.

McGrath suggested the current system allows "creation of entirely fictitious identities on the spot," and the photo ID requirement would stop that. He said politicians elected at the polls control billions of dollars, creating an incentive to cheat.

"Are we to believe no one would be tempted to steal something of that value?" McGrath said.

ID supporters suggested that probation records, death records and other databases could be accessed to quickly verify people's identities, but Jackson said such information is not easily available.

"There is no single database that tells us of people who are currently ineligible to vote because of felony convictions," Jackson said.

Carlson also said he would like to debate proponents around the state, because he believes the amendment makes major, unnecessary changes to an election system that is widely admired.

"Minnesota is looked upon nationally as the state for clean and open elections," he said. "We are the envy of this nation. These people have been painting a picture that is dark and getting darker by the minute."

Kiffmeyer, however, maintained that an ID requirement is needed to determine if there is a problem with voters using the identities of others. "Without an ID, how do you know?" she said. "Why do we have an election system that's based on catch and prosecute, and meantime the ballot is cast and counted?"

"My motive and my mission is about the integrity of the election system," Kiffmeyer added. "Through that process, I believe we can increase voter turnout."

The potential effect on voter turnout also is a key concern of amendment foes who contend it could discourage or prevent some groups from voting if they find getting a proper ID difficult or impossible.

"Elderly people are in a panic about this," Carlson said. "Students are in a panic."

McGrath responded that no legitimate voter would be denied a ballot through the photo ID requirement.

The photo ID ballot question will ask voters: "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?"

The underlying amendment, which will not appear on the ballot, also sets up a new system of two-step provisional balloting for those without the required ID, with the details to be determined by the 2013 Legislature. And it requires all voters, including those not voting in person, to submit to "substantially equivalent identity and eligibility verification."

The issue will appear on the ballot as a proposed amendment to the state Constitution, along with an amendment that would permanently ban same-sex marriage. The marriage amendment will the topic of a similar forum on Oct. 23 at the Maplewood Community Center.

Jim Ragsdale • 651-925-5042