Two people who worked as election clerks during the May 2016 primary runoff have pleaded guilty to unlawfully casting a ballot for another person, Harris County Clerk Stan Stanart announced Monday.

Jeanene Johnson, 63, and Latunia Thomas, 46, pleaded guilty to a misdemeanor charge of "unlawful deposit of ballot" earlier this month. They served one day in jail, and were released, according to the Harris County District Attorney's Office.

With Johnson's help, Thomas cast a ballot for her daughter at a Harris County Public Health and Environmental Services building during early voting for the May 24, 2016, primary runoff, according to Dane Schiller, a spokesman for the district attorney's office. He said Thomas' daughter was not present at the polling location.

"My office found convincing evidence that voter fraud was committed," Stanart, a Republican, said in a statement Monday. "The evidence was provided to the Harris County District Attorney's Office who presented the case to a Harris County Grand Jury."

Voter fraud allegations

Stanart's announcement comes amid allegations of rampant voter fraud, which have been used by Republican lawmakers across the country to ramp up controversial Voter ID laws. President Donald Trump has claimed that millions of people voted illegally for Hillary Clinton in the 2016 election, and this month has put together a commission to help study how many non-citizens illegally cast ballots.

In Texas, voter fraud was one of the central arguments behind the state's controversial 2011 Voter ID law, one of the strictest in the nation, requiring voters to present one of seven types of photo identification before being allowed to cast a ballot in person. Critics say the measure has no effect on mail-in ballots and accuse Republican lawmakers of trying to disenfranchise minority voters.

A federal judge in Corpus Christi last year ruled that the law was passed with discriminatory intent and violated the federal voting rights law. She reached the same conclusion earlier this year after a federal appeals court rejected part of her ruling claiming the law amounted to an illegal poll tax.

Lawmakers are working on a revamped version of the law, which Gov. Greg Abbott declared an emergency in the final days of the Texas legislative session.

Stanart said both Thomas and Johnson were election clerks hired to work the poll by the county at the recommendation of the Harris County Democratic Party.

Rare conviction

Lillie Schechter, who was elected chair of the Harris County Democratic Party earlier year, said she was not familiar with the incident as she was not chair when the crime took place. But she said the party will continue to take "voter fraud very seriously" and prioritize poll-watching and voter suppression.

Both defendants were charged with a felony, but pleaded guilty to a misdemeanor charge. The two were investigated after other clerks noticed the pair casting the ballot, Stanart said.

Stanart said that obtaining convictions on such crimes is rare. He said this month's convictions were the most significant finding and prosecution of voter fraud in the last decade-and-a-half.

The Texas Attorney Ggeneral's Office has received more than 700 reports of voter fraud since 2002, but has prosecuted only 93 since 2005.

"It's one thing to find it," Stanart said. "It's another thing to be able to have something where you could prove it."

An individual who answered a telephone number listed for Thomas referred questions to Thomas's attorney, who said she would not be able to reach her client Monday evening. Johnson could not be reached for comment Monday and her attorney said she could not respond to questions without speaking to Johnson.