At face value, an election on Tuesday will decide whether conservatives or liberals control the Wisconsin Supreme Court, a result that could shape the fate of essential policies in the state from abortion to congressional district maps.

But as a torrent of money from outside Wisconsin has made the contest the most expensive judicial race in American history, voters across the state said they had come to see this election to fill a single State Supreme Court seat more as a referendum on the early months of President Trump’s second term.

Fueling that perception is roughly $20 million that Elon Musk and groups allied with him have spent to boost the conservative candidate, Brad Schimel, a judge who also got President Trump’s endorsement not long ago. The liberal candidate, Susan Crawford, another judge, has decried Mr. Musk’s spending as an attempt to place a lackey on the state’s top court.

Whichever candidate wins will tip the seven-member high court’s political balance, which liberals currently control with a 4-to-3 majority.

But the outcome will also show how voters in one of the most evenly divided battleground states in the nation are feeling about Mr. Trump’s sharp cuts to the federal work force, his crackdown on illegal immigration and the administration’s crusade against diversity initiatives in government programs and higher education. Mr. Trump won Wisconsin by less than a percentage point last November and narrowly lost it in the 2020 election.

“The pendulum swings back and forth in U.S. elections, and I think this election will be a good indicator of whether the pendulum is going to swing back the other way based on Trump’s actions in office,” said Michael Orwig, 40, a federal worker and Schimel supporter who lives in a suburb south of Milwaukee. “This is going to be the first litmus test.”

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