Rep. Tom Tiffany, R-Wis., demanded an immediate investigation Tuesday after city of Madison officials said 2,215 duplicate ballots had been sent out across 10 wards in error.
Madison officials said the duplicate ballots have identical bar codes and so can't be counted twice.
"The City of Madison clerk said the duplicate absentee ballots were sent to one ward yesterday," Tiffany wrote on X. "Now, they say it’s 10. There needs to be an independent investigation now, not after the election."
Tiffany's office noted how the Madison clerk's office initially said duplicate ballots were sent to just one ward — but later came out saying the double ups span across all 10 "so their story changed."
"This can't just be swept under the rug," Tiffany said in a statement to Fox News Digital. "The people responsible for this need to be held accountable."
President Biden won Wisconsin, a key battleground state, by fewer than 21,000 votes in 2020.
Deputy Clerk of the City of Madison Jim Verbick cited how "there was a human error that occurred," impacting voters who had the same style or listed the same offices on their ballots, WKOW reported.
In a letter addressed to the City of Madison Clerk Maribeth Witzel-Behl, Tiffany said he was "demanding answers and transparency" on what happened, citing what he categorized as "the history of controversial and legally dubious election practices carried out by Madison officials in the past."
"Voters deserve clear answers regarding the full scope of this blunder, how the city plans to restore public confidence in its ability to accurately administer the election, and assurances that those responsible are held accountable," Tiffany wrote in the letter obtained by Fox News Digital.
Madison, the state capital, is considered a Democratic stronghold.
"A mistake was made, the Clerk's Office moved swiftly to rectify the error and reassure voters, but there is NO possibility of a duplicate absentee ballot being counted," city spokesperson Dylan Brogan told Fox News Digital.
The clerk's office described what happened as a "data processing error," explaining that the duplicate ballots have identical bar codes, so even if a voter submitted two absentee ballots, only one could be counted because the voting system does not accept the same bar code twice.
Also, once the ballot is scanned, the voter is marked in the poll book as having submitted an absentee ballot. That is another safeguard against the voter submitting a second ballot, the clerk’s office said.
Brogan said the mistake occurred when two identical files were merged, resulting in the creation of a list with double the names and double the addresses. Up to 2,000 duplicate ballots in one ward were mailed late last week before the mistake was caught and corrected. The clerk’s office has been contacting voters individually to notify them of the error and cautioning them to submit only one ballot, Brogan said.
"Despite duplicate ballots being sent out, we will only accept one ballot from every voter, and when we get them back we will make sure that we only have one ballot," Verbick said.
HARRIS-TRUMP SHOWDOWN: PRESIDENTIAL NOMINEES HIT KEY BATTLEGROUND STATES AS ELECTION APPROACHES
"About 3,000 voters all use the same ballot style, and we had to separate it into two different files to cover that range based on the limitation of the files that we can pull out of the registration system," Verbick told WKOW. "We tried to combine the two, and instead, one of them got copied instead of combined."
"I would just tell the voters that you can destroy one of the ballots," Verbick said. "Please do not send in both ballots, only one vote, one ballot, and the other can be destroyed."
When asked about Tiffany's letter, Verbick told WKOW, "I would just say that [the clerk's office] is very transparent about anything we do with elections, and I would just leave it at that."
CLICK HERE TO GET THE FOX NEWS APP
He added that no third party would be investigating the matter at this time.
Brogan told The Associated Press that Witzel-Behl was in the process of responding to Tiffany’s letter and "thoroughly answering all of these questions."
"It doesn’t matter if it’s Tom Tiffany, or who it is, we want everyone to know what happened," Brogan said.
As of Monday, Madison had sent 27,421 absentee ballots and none had been returned, according to the state elections commission. Brogan said none of the duplicate ballots had been returned since then.
The Associated Press contributed to this report.
