Several states adopted new laws last year requiring that people show a photo ID when they come to vote even though the kind of election fraud that the laws are intended to stamp out is rare.

Even supporters of the new laws are hard pressed to come up with large numbers of cases in which someone tried to vote under a false identify.

"I've compared this to the snake oil salesman. You got a cold? I got snake oil. Your foot aches? I got snake oil," said election law expert Justin Levitt, who wrote "The Truth About Voter Fraud" for The Brennan Center for Justice. "It doesn't seem to matter what the problem is, (voter) ID is being sold as the solution to a whole bunch of things it can't possibly solve."

Kansas, South Carolina, Tennessee, Texas and Wisconsin have passed laws this year that allow voters without the required photo ID to cast provisional ballots, but the voters must return to a specific location with that ID within a certain time limit for their ballots to count.

Indiana and Georgia already had such laws. Other states have photo ID laws too, but provide different way to verify a voter's identity without a photo ID. Texas and South Carolina are awaiting approval for their laws from the Justice Department because of those are among that states with a history of voting rights suppression and discrimination.

Indiana's law, passed in 2005, was upheld by the U.S. Supreme Court in 2008. Levitt combed through 250 cases of alleged election law fraud cited in legal briefs filed in that challenge. He found only nine instances involving a person allegedly voting in someone else's name, possibly fraudulently or possibly because of an error when the person signed in at the voting booth.

"They identified a lot of fraud, but very, very, very, very, very, very little of it could be prevented by identification at the polls," Levitt said.

The remainder involved vote buying, ballot-box stuffing, problems with absentee ballots, or ex-convicts voting even though laws bar them from doing so. Over the same seven-year time period covered by the cases Levitt reviewed, 400 million votes were cast in general elections.

"If there was evidence of this, we'd know about it," said Elisabeth MacNamara, president of the League of Women Voters. Her organization, which has affiliates in every state, knows voter registrars, attends election meetings, observes and works at polls and is intimately aware of how the election system works.

Hans von Spakovsky, a senior legal fellow at the Heritage Foundation, a conservative Washington think tank, said one reason there is scant evidence of voter fraud is no one checks ID at the polls. He cited a mid-1980s grand jury report that described how, over a 14-year period, "crews" were recruited in Brooklyn, N.Y., to vote multiple times in multiple elections at various polling places, using the names of real voters, dead voters, voters who had moved away and fictitious voters.

"Nobody's saying its large scale," but such fraud could make a difference in close races, said von Spakovsky, who led the Justice Department's civil rights division under President George W. Bush.

"It is something that happens in an instant and then it's gone," Republican Rep. Todd Rokita, who spent eight years as Indiana's secretary of state, testified during a recent Senate hearing. "Witnesses dissipate. These are volunteer poll workers. It's not a domestic violence case. It's not something that leaves visible scars or bruises. It's the kind of case that is very hard to prosecute. That doesn't mean it doesn't exist."

The laws and other voting restrictions have riled civil rights leaders and voter protection groups. Some groups say the new state laws are the equivalent of poll taxes and literacy tests that effectively kept minorities out of voting booths.

They argue that blacks, Hispanics, senior citizens, people with disabilities and the poor are more likely to lack the required photo ID. But they also contend others could be disenfranchised: voters who fail to bring ID with them; students whose school IDs are deemed unacceptable; people whose drivers' licenses have expired; women whose driver's licenses do not reflect their married names or new addresses.

"We basically see these voter ID restriction laws as a solution without a problem," said Judith Browne Dianis, co-director of The Advancement Project, a civil rights group.

Texas Attorney General Gregg Abbott, a Republican, launched an investigation in 2005 to uncover what he called an "epidemic" of voter fraud. But reviews of Abbott's investigation two years later yielded no cases of voter impersonation fraud. A Dallas Morning News review in 2008 found the 26 cases prosecuted were all against Democrats, most involved blacks and Hispanics, and typically involved people who helped elderly voters with mail-in ballots, but failed to follow state law by signing their names and addresses on the envelopes.

Abbot's investigation was paid for with a $1.4 million Justice Department crime-fighting grant.

After a five-year hunt for voter fraud, the Bush administration's Justice Department came up with little widespread fraud, finding mostly cases of people mistakenly filling out voter registration forms or voting when they didn't know they were ineligible, The New York Times reported in 2007. But none of the cases involved a person voting as someone else.

Lorraine Minnite, author of "The Myth of Voter Fraud," spent years researching voter fraud after finding that pushes for election reform often raised concerns that the proposed changes could lead to more voter fraud.

Her research turned up one case of voter impersonation from 2000 to 2005: A New Hampshire teenager who cast a ballot as his father, who shared the same name. Minnite said she concluded "the whole problem is way overblown" largely for political reasons.

Asked by The Associated Press for examples of unprosecuted cases, Rokita's office pointed to suspicious or poorly filled out voter registration cards submitted in 2008 by the now-defunct community activist group ACORN. Rokita's spokesman Timothy Edson said the Indiana photo ID law prevented people from fraudulently voting under those registration cards.

But Illinois Democratic Sen. Dick Durbin, who led the hearing where Rokita testified and opposes the photo requirement, insisted such fraud should be prosecuted if it is happening frequently enough to warrant the new laws.

"There ought to be a clear example to the people of this country we just won't stand for this wherever it might occur," Durbin said.