(CNN) — Wisconsin voters on Tuesday will decide the outcome of a state Supreme Court race that could be the most consequential election of the year.

The race between Democratic-backed Milwaukee County Circuit Court Judge Janet Protasiewicz and Republican-backed former state Supreme Court Justice Daniel Kelly could both break a decadelong era of Republican dominance in one of the nation's most important swing states and prove pivotal in the fight over the future of abortion access. It's the most expensive state judicial race ever.

Conservatives currently hold a 4-3 majority on the Wisconsin high court. But the retirement of conservative Justice Patience Roggensack has given liberals an opening to retake control for at least the next two years, and with it fundamentally shift the political landscape in a state that has been ensnared in political conflict for more than a decade. The race could also effectively decide how the court will rule on legal challenges to Wisconsin's 1849 law banning abortion — which took effect after the US Supreme Court overturned Roe v. Wade last summer.

Wisconsin is one of 14 states that directly elect their Supreme Court justices, and winners get 10-year terms. The races are nominally nonpartisan, but political parties leave little doubt as to which candidates they support. Spending in this year's race — which reached $28.8 million as of March 29, according to the Brennan Center — has far surpassed the previous record for spending on a state judicial contest: $15.4 million in a 2004 Illinois race.

Republican sway in Wisconsin began with Gov. Scott Walker's election in 2010 — a victory that was followed by the passage of union-busting laws and state legislative districts drawn to effectively ensure GOP majorities, all green-lit by a state Supreme Court where conservatives have held the majority since 2008.

Walker lost his bid for a third term to Democratic Gov. Tony Evers in 2018. But Evers has been hamstrung by the Republican-led legislature, with the conservative Supreme Court breaking ties on matters such as a 2022 ruling during the once-a-decade redistricting process in favor of using Republican-drawn legislative maps rather than ones submitted by Evers. The decision cemented Republicans' solid majority in the state legislature.

Revisiting those maps, which Protasiewicz has criticized, could lead to new state legislative districts that are less favorable to Republicans if she is victorious.

The court has also shaped Wisconsin elections in other ways. It barred the use of most ballot drop boxes last year and ruled that no one can return a ballot in person on behalf of another voter. The court played a pivotal role in the outcome of the 2020 election in Wisconsin: Justices voted 4-3, with conservative Brian Hagedorn joining the court's three liberals, to reject former President Donald Trump's efforts to throw out ballots in Democratic-leaning counties.

Tuesday's election will set the stage for the 2024 presidential race, with the court likely to be asked to weigh in again on election rules, including the state's voter identification law, and potentially sort through another round of legal challenges afterward.

But the most immediate battle likely to reach the justices as early as this fall is over Wisconsin's 1849 law that bans abortion in nearly all circumstances.

Groups on both sides of the abortion divide have poured vast sums into the race and have attempted to mobilize voters ahead of Tuesday's election.

Though the two candidates have refused to say how they'd rule on the issue, they've left little doubt about their leanings.

In a debate last month, Protasiewicz said she was "making no promises" on how she would rule. But she also noted her personal support for abortion rights, as well as endorsements from pro-abortion rights groups. And she pointed to Kelly's endorsement by Wisconsin Right to Life, which opposes abortion rights.

"If my opponent is elected, I can tell you with 100 percent certainty, that 1849 abortion ban will stay on the books. I can tell you that," Protasiewicz said.

Kelly, who has done legal work for Wisconsin Right to Life, shot back, saying Protasiewicz's comments were "absolutely not true."

"You don't know what I'm thinking about that abortion ban," he said. "You have no idea. These things you do not know."

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