MADISON, Wis. (AP) — A fourth Wisconsin voter out of roughly 3 million who cast ballots in the 2020 presidential election was charged with election fraud on Thursday by a Republican prosecutor who is running for attorney general.

Fond du Lac District Attorney Eric Toney said the charge alleging that a felon voted illegally does not mean that the election won by President Joe Biden was stolen. The criminal complaint does not identify whether the person charged is a Republican or Democrat or who he voted for in the presidential election.

“But elections are the cornerstone of our democracy and the integrity of our electoral process must be protected at every turn,” Toney said in a statement. “We will continue to prosecute any circumstances of voter fraud, as allowed by law, in order to safeguard our electoral process and ensure the public has confidence in our elections.”

Wisconsin Republicans, fueled by anger and the lie that the 2020 presidential election was stolen from former President Donald Trump, have ordered two separate investigations in the battleground state Biden won by fewer than 21,000 votes. One is underway by the nonpartisan Legislative Audit Bureau. The other was ordered by Assembly Speaker Robin Vos and is being led by former conservative Wisconsin Supreme Court Justice Michael Gableman.

Charges of election fraud are exceedingly rare in Wisconsin, but there typically are a handful after every major election. The crime of election fraud is a felony.

Only three other people have been charged to date with fraud related to the November election.

In one case, out of St. Croix County, a 64-year-old man faces four felony charges for casting two absentee ballots. A preliminary hearing in that case is set for Monday. In Sawyer County, a 36-year-old Florida man was charged with election fraud after unsuccessfully trying to obtain an absentee ballot by falsely claiming he was a resident of the village of Radisson. A preliminary hearing in that case is set for Oct. 11. In a third case, a 49-year-old Cedarburg woman faces two felony charges after prosecutors say she submitted an absentee ballot close to Election Day for her life partner who had died months earlier. Trial is set to begin Oct. 12.

In the latest case, prosecutors allege that 63-year-old Donald Holz voted illegally in Fond du Lac because he was a convicted felon who had not completed the terms of his probation. He faces a $10,000 fine and up to three years and six months in prison if convicted.

According to the complaint, Holz told investigators that he “went ‘online’ and as far as he knew it was ok for him to vote.” Holz said he told election workers he was on probation and doesn’t know why they let him vote if he wasn’t allowed to, the complaint said.

“Holz stated he wished he had called his probation agent to determine if he was eligible to vote,” the complaint said.

The prosecutor, Toney, is running against University of Wisconsin professor Ryan Owens in the Republican primary for attorney general in 2022. The winner will face Democratic Attorney General Josh Kaul, who on Thursday dismissed the GOP election investigation as chasing conspiracy theories.