The election for a swing seat on the court is likely to determine whether abortion remains illegal in Wisconsin, as well as the future of the state’s heavily gerrymandered political maps. Daniel Kelly, a conservative former State Supreme Court justice, is running against Janet Protasiewicz, a liberal Milwaukee County judge, for a pivotal seat on the state’s high court.Credit...Jamie Kelter Davis for The New York Times

WAUKESHA, Wis. — American political candidates routinely drum up support by warning voters that this election, really, is the most important of their lifetimes.

It’s almost always an exaggeration, but the description might just fit for Wisconsin’s deeply polarized voters, who on Tuesday will choose a justice to fill a swing seat on the state’s Supreme Court.

The winner — either Janet Protasiewicz, a liberal Milwaukee County judge, or Daniel Kelly, a conservative former State Supreme Court justice — will have the deciding vote on a host of major issues, including abortion rights, gerrymandered political maps, and voting and election cases surrounding the 2024 presidential contest.

Officials on both sides have described the stakes of the officially nonpartisan race in existential terms — either they win and democracy survives, or they lose and it perishes.

Wisconsin Democrats, who have been lost in the political wilderness for a dozen years, cast Judge Protasiewicz as their path to a promised land of abortion rights and fair maps. The state’s Republicans say Justice Kelly is their last hope to ward off liberal tyranny by fiat.

Here are four themes animating Tuesday’s election:

Wisconsin could turn sharply back to the left — or not. Wisconsin Republicans tend to talk about the election as if Judge Protasiewicz would roll onto the Supreme Court with a giant eraser to wipe out all of the legislative policies and structural advantages the G.O.P. has built for itself since Scott Walker became governor in 2011. 

They’re not entirely wrong.

“A lot of the duly passed laws by the elected representatives of the state of Wisconsin would be deemed invalid,” Duey Stroebel, a Republican state senator from Cedarburg, said last week. “It wouldn’t be the people electing their representatives that would be making decisions, it would be her, based on her personal beliefs.”

Indeed, Judge Protasiewicz has been clear about her views. She has signaled her opposition to Wisconsin’s 1849 law banning abortion in nearly all cases, which went back into effect when the Supreme Court overturned Roe v. Wade last summer, and she has called the legislative maps Republicans drew to give themselves a durable near-supermajority in the State Legislature “rigged” and “unfair.”But the state’s Democrats sound similarly apocalyptic about the prospect of Justice Kelly, who lost a 2020 bid to retain his seat on the court, returning to deliver conservatives a majority. He is aligned with the state’s anti-abortion groups and has said there is no legal problem with the maps.