WASHINGTON, April 1, 2025 (BSS/AFP) - Donald Trump's tumultuous return to the White House will face a popularity test Tuesday with an election in Wisconsin that has seen the US president's most high-profile aide Elon Musk doling out million-dollar checks to voters.

Since taking power in January, Trump has overseen radical reform, moving to dismantle swaths of the federal government, upending foreign policy and launching trade wars that threaten to reignite inflation.

The president's targeting of migrants, judges, "woke" culture and any critics have been lauded by his supporters, but have not yet faced a major test among voters.

Wisconsin's election of a judge to join the state's supreme court pits conservative Brad Schimel against liberal Susan Crawford.

The outgoing judge was backed by Democrats, so a Schimel win would tilt the court right, while Crawford would preserve its liberal leanings.

Musk has argued that a conservative win is needed to cement Trump's national agenda, with the supreme court race having an impact on a potential redrawing of Congressional districts in the swing state ahead of midterm elections next year.

Trump's Republican party in Washington holds a slim 218-213 majority in the House of Representatives over Democrats, and an even slimmer lead in the Senate.

Trump attacked Crawford on social media on Monday, accusing her of "letting child molesters and rapists off easy."

"She will be one of the most Liberal Judges ever elected, which would be a DISASTER for Wisconsin and, the United States of America," he said.

Also on Tuesday, voters in Florida will elect members of the House in two heavily Republican districts, which were vacated by Trump's National Security Advisor Mike Waltz and his original nominee for attorney general, Matt Gaetz.

- Most expensive race -

The Wisconsin poll is expected to be close, with Trump narrowly beating his Democratic rival Kamala Harris in last year's presidential election by less than 30,000 votes in the state.

Musk, who spent roughly $277 million on Trump's election campaign, has piled more resources into the Wisconsin vote.

He has handed out two prize checks of $1 million each to voters, and also given $100 each to voters who sign his petition against "activist judges."

According to the Brennan Center for Justice, more than $49.7 million has been spent by Schimel and his backers, including $12.2 million from Musk's America PAC.

Crawford's campaign and those backing her have spent an estimated $40.3 million.

The spending has made the Wisconsin race the most expensive in US judicial history, the center said.

Crawford has accused Tesla owner Musk of seeking to buy a seat on the state supreme court to swing judgments in favor of his companies.

A case regarding car dealerships filed by the electric vehicle manufacturer is potentially headed to the court.

Speaking at a campaign rally on Sunday, Musk placed the national political context front and center.

"What's happening on Tuesday is a vote for which party controls the US House of Representatives," Musk declared, arguing that the Congress was so evenly balanced that Wisconsin's seats could decide its majority in the 2026 midterms.

The billionaire's Green Bay rally had an enthusiastic crowd, but the South African-born oligarch's role in Wisconsin elections has provoked as much resistance as support.

At a pro-Crawford rally, 65-year-old retired electrical engineer Rob Patterson held up a sign showing Musk giving a straight-armed salute.

"Our Supreme Court is not for sale," the sign read.