(CNN) Democrats claimed victory Monday in a Wisconsin Supreme Court election that Republicans insisted on holding last week despite the coronavirus pandemic.

Liberal Dane County Judge Jill Karofsky defeated conservative Justice Daniel Kelly, an incumbent backed by President Donald Trump, in a race for a 10-year seat on the state's Supreme Court. Karofsky declared victory and Kelly conceded Monday evening as votes were still being counted in the close contest.

The outcome is an embarrassment for state and national Republicans, who had blocked Democratic Gov. Tony Evers' bid to postpone the election or have it conducted entirely by mail and had fought in court against rules that would have made it easier to cast absentee ballots -- leaving Wisconsin the only state to go forward with in-person voting in April.

A federal judge had ordered Wisconsin to wait six days before counting the votes cast last Tuesday, giving absentee ballots that were postmarked by election day time to arrive at clerks' offices.

Republican state Assembly Speaker Robin Vos and Senate Majority Leader Scott Fitzgerald's insistence on in-person voting led to long lines in Democratic strongholds like Milwaukee, where the city reduced its planned 180 polling places to just five that were open on election day.

Vos volunteered as a poll worker in Burlington, appearing in full protective gear -- gloves, a mask and a gown -- while telling voters that "you are incredibly safe to go out."

Vos and Fitzgerald rejected Evers' request 11 days before the election to mail every voter a ballot, then asked the Republican-dominated state Supreme Court to halt Evers' executive order the day before the election that would have postponed it until June.

Though Kelly did not vote, he tweeted his support for the Republican effort to overturn Evers' order.

"We can do two things at the same time: maintain the foundations of our democracy while taking reasonable precautions to keep people safe," he tweeted.

Meanwhile, the Republican National Committee and the Republican Party of Wisconsin, acting on behalf of state legislative leaders, successfully appealed to the US Supreme Court a federal judge's decision to extend the deadline for absentee ballots to be returned. The court ruled that ballots must be postmarked by election day on April 7 -- even though on the morning of the election, local clerks had not even mailed ballots to more than 11,000 people who had requested them on time.

Even after votes had been cast last week, Karofsky told the Milwaukee Journal Sentinel that the primary should have been delayed.

"They wanted to suppress votes and they succeeded in suppressing votes," she said.

Karofsky's victory reduces the conservative majority on Wisconsin's high court to 4-3. It could also position Karofsky to cast the deciding vote in a closely watched case over a GOP effort to purge the state's voter rolls of more than 230,000 people who could have moved.

That case could have implications for November's presidential election: Trump won Wisconsin by about 22,000 votes in 2016, and the state is again certain to be a marquee battleground between him and former Vice President Joe Biden, the presumptive Democratic nominee. Biden will win the Democratic presidential primary in the state, CNN projects.

The election was the first battle over voting rights amid a crisis that led so many poll workers to quit that Evers had ordered Wisconsin National Guard members to work at polling places on election day.

Earlier Monday, Wisconsin and national Democrats had suggested they were considering further challenges to the election.

Ben Wikler, the Wisconsin Democratic chairman, said the party will "find every possible path for protecting voters."

Democratic National Committee Chairman Tom Perez called Wisconsin Republicans' insistence on going forward with the election "voter suppression on steroids, because it was putting people's lives in danger."

He said he believed there were thousands of people in Wisconsin who had requested absentee ballots before the state's deadline, but did not receive those ballots in time to vote.

"It's impossible to submit an absentee ballot by election day when you haven't even received the damn ballot by election day," Perez said.

Wisconsin's election was also the final Democratic primary before Vermont Sen. Bernie Sanders dropped out of the race, making Biden the party's presumptive nominee.

This story and its headline have been updated with additional information about last week's election.