The last time Wisconsin held an election for the state’s Supreme Court, Republicans cried foul over the wave of money from out-of-state Democrats that overwhelmed their candidate.

Two years later, Republicans have learned their lesson. It is Democrats who are grappling with a flood of outside money inundating Wisconsin.

A super PAC funded by Elon Musk has in just the past week spent $2.3 million on text messages, digital advertisements and paid canvassers to remind Wisconsin Republicans about the April 1 election, which pits Brad Schimel, a judge in Waukesha County and a former Republican state attorney general, against Susan Crawford, a Dane County judge who represented Planned Parenthood and other liberal causes in her private practice.

The spending by Mr. Musk, the tech billionaire who is leading President Trump’s project to eviscerate large segments of the federal government, comes as Judge Schimel and his Republican allies have spent more money on television ads than Judge Crawford and Democrats have — a remarkable turnaround in a state where Democrats have had a significant financial advantage in recent years.

“When I was a little girl growing up in Chippewa Falls, I never could have imagined that I’d be fighting the world’s richest man,” Judge Crawford told a crowd over the weekend at a campaign stop in Cambridge, Wis.

As of Monday, Republicans had spent or reserved $13.9 million of television advertising time for the Wisconsin court race, compared with $10.7 million for Democrats, according to AdImpact, a media-tracking firm. Because a larger chunk of Republican spending comes from super PACs, which pay a higher rate for TV ads than candidates do, the amount of advertising on Wisconsin’s airwaves has remained roughly equal. But the heavy Republican spending has eliminated what was a significant advantage for Democrats in the last such contest, in 2023.