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The Wisconsin Supreme Court told election officials across the state on Thursday – a week before the deadline to mail ballots – that they can’t mail out absentee ballots until the court decides whether to add the Green Party’s presidential ticket to the ballot.

The September 17 deadline for when the 1,850 municipal clerks need to mail out absentee ballots to Wisconsin voters who asked for one is set in state law.

The 4-3 decision by the Wisconsin Supreme Court was split among partisan lines, with all four conservative justices agreeing that the process of mailing out ballots must be paused, while the three liberal justices dissented. The possible inclusion of Green Party presidential candidate Howie Hawkins on the general election ballot could tip the scales of a razor-thin contest between President Donald Trump and Democratic nominee Joe Biden.

Related: Understanding mail-in voting in the US

Voting during the pandemic in Wisconsin has already been the subject of legal fights. Republicans who insisted on keeping the state’s April 7 primary on schedule won two legal battles in the spring, as the state Supreme Court blocked Democratic Gov. Tony Evers’ bid to delay it until June and the US Supreme Court reversed a lower court’s ruling that gave voters six extra days to return their ballots by mail. At least 19 people in Wisconsin who said they voted in-person or worked the polls tested positive for the coronavirus, according to the state health department later that month.

About 1 million voters in Wisconsin have requested ballots, and more than 378,000 of those ballots have already been prepared by local clerks to go out to voters, and some have been sent out, according to the Wisconsin Election Commission, which says it scrambled to collect data from thousands of local officials to comply with the court’s order.

One clerk said it “will not be attainable” to meet the deadline if the court says ballots need to be re-printed. Another said it was “unfair” for the court to put clerks in this position so close to the deadline. Others said it would be expensive to re-print ballots at this late stage, and one clerk warned of widespread “voter confusion,” saying, “we are too far in the process for this to occur.”

When asked what would happen if the justices order another candidate to be added to the ballots after they have already been printed, Meagan Wolfe, the chief elections official for the state of Wisconsin, who was speaking to reporters on a media call when the court order came down, said that “it would be incredibly complicated and difficult.”

Wolfe told the court that she doesn’t know how many ballots have actually been sent to voters.

Hawkins was one of two candidates that was denied a position on the general election ballot by the Wisconsin Election Commission. The other is rapper Kanye West, who has filed a lawsuit seeking to overturn that decision. The lawsuit is still pending and could also impact the ballot-printing process.

Attorney Jeffrey Mandell, who is representing one of the people who sued to keep Hawkins off the ballot, said that changing the ballots at this point would inject uncertainty into an already fragile 2020 election process.

“This could lead to unprecedented chaos,” Mandell said.

In 2016, Green Party candidate Jill Stein received 31,072 votes in Wisconsin. That tally is greater than the 22,748-vote margin that handed Trump a victory in the state over Democratic nominee Hillary Clinton.

This story has been updated with details of ballots sent out and reaction from local clerks in court filings.

CNN’s Caroline Kelly, Eric Bradner, Veronica Stracqualursi, Marshall Cohen and Abby Phillip contributed to this report.