Originally Published: 21 FEB 23 07:00 ET

Updated: 21 FEB 23 08:50 ET

By Tierney Sneed, Fredreka Schouten and Eric Bradner, CNN

(CNN) -- Wisconsin voters on Tuesday will cast their primary ballots in what's turned into an expensive and high-stakes battle for control of the state Supreme Court in a key political battleground where power is divided between a Democratic governor and a Republican-controlled legislature.

Voters will narrow the field of candidates down to two, who will then advance to April's general election for a seat on a court where conservatives currently hold a 4-3 majority. Although the election is technically nonpartisan -- there are no party labels on the ballot -- interest groups align, party operations mobilize and money flows into races for its seats as if they were partisan contests.

The departure of a conservative justice, Patience Roggensack, has given liberals an opportunity to seize the majority on a court that could decide on issues such as abortion, redistricting, and voting rights ahead of the 2024 presidential election.

Conservatives have controlled the state's high court for 14 years -- a span in which the court has sided with Republicans' union-busting efforts and affirmed voting restrictions, including ID requirements and a ban on ballot drop boxes.

"This seat is crucial to the balance of the court, and the court is crucial to the balance of the state," said Barry Burden, a political scientist at the University of Wisconsin-Madison and director of its Elections Research Center.

The candidates hoping to advance to the April general election are liberals Janet Protasiewicz, a Milwaukee County circuit court judge, and Everett Mitchell, a circuit judge in Dane County; and conservatives Daniel Kelly, a former state Supreme Court justice, and Jennifer Dorow, a judge perhaps best known for presiding over the trial of a man convicted of killing six and injuring scores more in a 2021 attack on a Christmas parade in Waukesha, Wisconsin.

Outside money has flooded the race, surpassing candidate spending. As of Thursday afternoon, orders for TV and radio ads focused on the race had hit $7 million, according to advertising tracked by Kantar Media/CMAG for the Brennan Center for Justice at New York University's law school. Experts say the spending on the race could smash the previous record -- $15.2 million spent on a 2004 Illinois Supreme Court race, according to the liberal-leaning Brennan Center -- for the most expensive campaign for a single state Supreme Court seat.

The court could become the final arbiter on a host of critical issues in Wisconsin in the coming years -- including the fate of the state's 1849 law prohibiting abortion in nearly all cases. The US Supreme Court's decision last summer ending federal legal protections for the procedure has super-charged the rhetoric -- and spending -- around abortion in the Wisconsin race.

The state Supreme Court could also play a crucial role in the 2024 election. Wisconsin was a key location of former President Donald Trump's attempts to overturn his 2020 loss, and the refusal of a conservative justice on the state Supreme Court to go along with an effort that year to toss out ballots in two heavily Democratic counties looms large in the rivalry between the two right-leaning candidates in this year's race.