(CNN) In the final weeks of the campaign as Donald Trump fuels questions concerning voting irregularities, a case in Indiana -- the home turf of the GOP running mate Mike Pence -- perfectly frames the current debate on voter fraud.

On the one side of the controversy are those who say they are working to protect the integrity of the election. On the other side are their opponents who allege that some of those efforts are really a veiled attempt to restrict the vote.

The issue in Indiana is Patriot Majority USA, a liberal group that runs the Indiana Voter Registration Program, which calls itself the largest voter registration program of African-Americans in the state. It says it submitted some 40,000 registration forms this year — until Republican officials stepped in.

"We were succeeding in registering tens of thousands of voters," said the group's president, Craig Varoga.

In early October, the Indiana State Police announced that it had expanded an earlier probe involving the group investigating forms that had missing, incomplete and incorrect information. Although the investigation started out in only a handful of counties, it expended to cover 56 of them. Police also obtained and executed a search warrant for the Indianapolis offices of the Indiana Voter Registration Project.

Pence brought up the issue while on the campaign trail in New Mexico last week.

"Voter fraud?" Pence said, "we've got that in Indiana."

Last week, Secretary of State Connie Lawson alerted the media that her office received number of calls from voters who had voted in the May 3 primary, but found that their date of birth or first name had been changed when they went back to check their registration.

"We looked onto the Statewide Voter Registration System and noticed that there had been an unusually high number of date of birth and first name changes," the secretary of state's office told CNN last week. There are only three ways to make changes to voter registration records in the state: (1) on paper forms submitted to the county election office; (2) on paper forms submitted to the Bureau of Motor Vehicles and later sent to the county election office; or (3) online at Indianavoters.com. The secretary of state's office found that the thousands of changes in this case were made in all three ways, but officials do not believe the registration system was hacked.

"We believe this may be a case of voter fraud and have turned our findings over to the State Police, who are currently conducting an investigation into alleged voter fraud," she said.

State Police Superintendent Doug Carter said Lawson's information was "consistent" with its ongoing investigation.

"Let me be clear: Among the highest priorities of the Indiana State Police is ensuring the integrity of this election," Carter said in a statement.

The results of the investigation are unlikely to be completed before Election Day, Carter said.

Varoga and Indiana Democrats believe the actions by Carter and Lawson are politically motivated.

William Groth, who has represented Democrats in various election related issues, questions whether Carter, a Pence nominee, and Lawson, a Republican with ties to Pence, might be playing politics. "My suspicion is that this is all being ginned up by Mike Pence to support some of his running mates' claims that the system is rigged," he said.

Lawson addressed such accusations in a statement. "For anyone to suggest I am playing politics with voter registration is absurd," she said.

In an interview with WIBC Tuesday , Carter defended the investigation, noting it started with a case in Hendricks County, not from the secretary of state's office. "This will not be driven by politics. It will be driven by process and what we are expected to do legally and that's exactly what we'll do," he said.

Carter said he hasn't spoken to Pence about the probe.

"I wish people knew Mike Pence like me," Carter said. "The thought that he would come to me and make this dark, shady deal to do something that he knew was wrong is as unconscionable as anything I've ever heard in my entire adult life. I have not talked to Mike Pence about this...and I'm going to be very frank with you: the notion that he would try and influence this is crazy."

Varoga doesn't see things the same way. Patriot Majority launched a statewide campaign to raise awareness of what it called a "partisan effort to disenfranchise 45,000 new Hoosier voters, most of whom are African-American."

"This Republican effort to suppress the vote is a violation of civil rights, but it is also a dangerous and cynical move that undermines law-enforcement's relations with its own citizens," he said in a statement.

Rick Hasen, an election law expert of University of California-Irvine, stresses that in general even if there is voter registration fraud, that doesn't translate to in-person fraud at the polls.

In a recent blog post, he summed it up: "I never say voter fraud is non -existent," he said and noted that it happens occasionally with absentee ballots and that action needs to be taken to clean up voter registration rolls.

"What is extremely rare and has not affected any election we know of since the 1980's is impersonation fraud," he said.

Hasen is critical of Trump statements on the campaign trail.

"Trump is undermining our faith in democracy itself by making irresponsible claims the election could be rigged through voter impersonation fraud and urging his followers, untrained to go to polls in 'certain areas' to ferret out voter fraud," Hasen said.

Like others, Hasen is taking a wait-and-see approach on the Indiana case until Carter's investigation is complete.

"It's a puzzling case," said Marjorie Hersey, a professor at Indiana University.

"By law, any groups that register voters are required to turn in all the registrations they receive, to make sure that they don't decide to turn in only the forms of prospective voters who favor their party," she said.

It's not infrequent for a state to receive a number of inaccurate registration forms, Hersey said. She is worried that voters might hear allegations of voter fraud and be under the impression that "the old-time, cigar-chomping city 'bosses' that held power in many cities in the late 1800s and early 1900s are still alive and well."

"Once people get a colorful image in their minds, it's not easy to convince them of the reality of today's elections," she said.