Hundreds of absentee ballots mailed back to the City of Madison for Tuesday's election may not be counted, thanks to a missing postmark.

The problem is one that is emerging in communities across Wisconsin as election officials prepare to tally the results of an election conducted during the coronavirus pandemic. Results for the state Supreme Court and other races are to be released Monday.

The issue has surfaced because of a surge in mail voting and a U.S. Supreme Court ruling on the eve of the election that requires absentee ballots to be postmarked by election day, April 7, if they arrive after that.

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Madison City Clerk Maribeth Witzel-Behl said that so far her office has received more than 8,000 absentee ballots. Of those, 682 have no postmark, meaning that it's likely they won't be counted.

She said seeing the ballots come in without the postmark has been frustrating, especially since the ballots that came in on Wednesday were likely mailed before Tuesday.

"It's heartbreaking to see that many of them have no postmark," she said. "That's not the fault of the voter. The voter has no control over that."

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Witzel-Behl said that she isn't sure yet what will happen, but she's seeking legal guidance and clarification.

Nearly 1.3 million absentee ballots were requested for Tuesday's election, according to the Wisconsin Elections Commission. As of Friday morning, 1.08 million of those ballots had been returned.

A postmark is a marking put over a stamp on a piece of mail at the post office where it's received, often showing the location and date, according to information on the United States Postal Service website. The postmark cancels the stamp affixed to the mail so that it can't later be peeled off and reused.

But in many cases, postmarks are not used, such as for metered mail.

Robert Sheehan, a Wisconsin media contact for the Postal Service, said the issue of absentee ballots without postmarks was being investigated but he declined to address other questions.

State statutes do not require absentee ballots to be postmarked. During a normal election, absentee ballots must be received by clerks by 8 p.m. on election day to be counted. If the ballot arrives after then, it cannot be counted.

But last week, U.S. District Judge William Conley ruled absentee ballots could count as long as they were received by clerks by April 13 — six days after election day — regardless of when they were sent. Republicans appealed part of that decision and the U.S. Supreme Court in a 5-4 decision sided with them late Monday and required that absentee ballots had to be in clerks' hands by the next day or postmarked by then.

Conley didn't put a postmark requirement in place because he knew thousands of voters wouldn't receive their absentee ballots until after election day. But the Supreme Court said it was essential to have postmarks for late-arriving ballots to make sure they were cast before election day.

During a Friday meeting of the bipartisan state Elections Commission, Democrats tried to have more absentee ballots counted, but Republicans said they had little ability to do that because of the U.S. Supreme Court decision.

The commissioners unanimously agreed to count absentee ballots that arrived after election day that were stamped with a certain circular postmark if the U.S. Postal Service provides a written statement saying that postmark was used only on election day.

But Democrats said the commission should count a broader set of absentee ballots, including all of those that arrived Wednesday because they would have been in the mail by election day.

In many cases postmarks are nothing more than “decorative stamps” that don’t provide information about when mail was processed, said Ann Jacobs, one of the Democratic commissioners.

“How many people are we going to disenfranchise for a decorative stamp vs. actually having put their ballot in on time?” she said. “Those votes ought to be being counted.”

But the commission’s Republican chairman, Dean Knudson, said the commission had to go by what the Supreme Court said about postmarks.

“This is the problem with having court rulings on the eve of the election — is that it’s hard for us to get word out to people as to what that’s going to mean for them,” he said.

Scott Van Derven, president of the Wisconsin State Association of Letter Carriers, said in an interview that all absentee ballots delivered on Wednesday would have had to have been mailed on Tuesday or earlier. Mail is processed at the end of the day and there would be no way for someone to put an absentee ballot in the mail on Wednesday and have it delivered that same day, he said.

Postmarks aren't the only issue with absentee ballots across the state. On Wednesday, attention was drawn to three tubs of undelivered ballots in a mail processing center that were meant for voters in Appleton and Oshkosh. Separately, the Milwaukee Elections Commission called for an investigation into other ballots that never made it to voters.

And in Fox Point, hundreds of undelivered ballots were sent back to the village, unopened and unmarked. No explanation was given as to what was wrong with the ballots, or why they couldn't be delivered.

No details have been released about how many voters didn't get absentee ballots, or how many of those who didn't receive them ended up voting in person instead.

So far, election officials have been left mostly in the dark, said Meagan Wolfe, the director of the Wisconsin Elections Commission.

“We are having a really hard time getting any answer from the Postal Service themselves,” she said.

U.S. Sens. Tammy Baldwin and Ron Johnson are calling for an investigation into the missing ballots in the state, asking the United States Postal Service's inspector general to identify what went wrong, as well as look into the issue of missing postmarks.

Postmark problems around the state

Clerks are reporting concerns about missing postmarks across the state.

In Shorewood, Village Clerk Sara Bruckman said more than 500 postmarked ballots have arrived in the two days following the election. About a dozen did not have a postmark or the postmark was illegible.

In Manitowoc, Clerk Deborah Neuser wasn't sure how many ballots her office had received since Tuesday, but noted that not all of them had postmarks on them. Those ballots, she said, will be referred to the Municipal Board of Canvassers on April 13.

In Greenfield, 243 absentee ballots out of 9,330 were without a postmark, said clerk Jennifer Goergen.

In Luxemburg, Village Clerk MiLissa Stipe said the postmarks on the envelopes were so light that she couldn't read the date on them. Elm Grove had a similar issue — so far 34 ballots have been returned with no postmark or with a postmark that is not readable, according to the clerk.

In Fitchburg, 41 ballots out of 488 returned so far don't have a postmark on them, said clerk Tracy Oldenburg.

In Sister Bay, Clerk Heidi Tech said that six absentee ballots were received on Wednesday without a postmark. Thursday, she received four ballots, all postmarked on April 7.

Diana Dykstra, village clerk of Mukwonago, said she noticed, too, that absentee ballots were being returned with handwritten postmarks, unlike during normal elections.

"Normally when ballots arrive here they do not have a 'hand cancel' or postmark on them," she said. "The post office has always just delivered them to us and we have our indicia on the envelope where we paid for the postage for them to return."

In Suring, out of the 96 absentee ballots that have been received, two have been returned with an April 8 postmark and won't be counted, clerk Carol Heise said.

Alisa Schafer, Chris Clough, Samantha Gibbons, Kent Tempus, James Riccioli, Robert Dohr and Jeffrey Rumage of the USA TODAY NETWORK-Wisconsin contributed to this report.

Laura Schulte can be reached at leschulte@gannett.com and twitter.com/SchulteLaura.