Washington DC - Donald Trump's rampaging presidency faced its first electoral test Tuesday in an election to Wisconsin's Supreme Court and a pair of House races in Florida, one of which US media has reported stayed in Republican hands.

Trump has gone all out to boost his party's chances in the contests and sent his controversial, hugely powerful advisor Elon Musk – the world's richest man – to sway the vote in Wisconsin.

Now, after two months in which the Trump-Musk tandem has appeared nearly unstoppable, Americans were giving a verdict of sorts.

Trump again pushed Tuesday for the conservative judge running for the spot on Wisconsin's top court, saying on social media that Brad Schimel was a "Patriot" while his liberal opponent Susan Crawford is a "Radical Left Liberal."

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Echoing his usual extreme rhetoric, Trump claimed Crawford has a "History of letting child molesters and rapists off" and that a win by her would be a "DISASTER."

Musk, who has spearheaded Trump's radical attempts to gut much of the US government in a right-wing cost-cutting drive, went himself to Wisconsin to drum up support for Schimel.

"It's like one of those strange situations where a seemingly small election would determine the fate of Western civilization here," Musk said in a discussion on his social media platform X on Tuesday.

The highlight of his weekend visit to the upper Midwestern state reprised a tactic seen during his efforts to help Trump defeat Democrat Kamala Harris in November – handing out money to anyone who signed a petition against so-called "activist judges."

Senator Bernie Sanders, a major force on the left of the Democratic Party, told supporters on X they had "the power to REJECT Musk and the oligarchy buying our elections. Send a powerful message to the whole country. Vote today for Susan Crawford."

Beyond testing the public mood, the Wisconsin result will decide whether the state's Supreme Court – which rules on things like voting district boundaries – tilts majority left or right.

In Florida, two seats in the US House of Representatives were up for grabs to fill vacancies left by Trump's National Security Advisor Mike Waltz and failed nominee for attorney general, Matt Gaetz.

On Tuesday evening, US media called the race for Florida's sixth district in favor of Republican Randy Fine, with Trump tweeting: "Congratulations Randy, a great WIN against a massive CASH AVALANCHE."

Democrats will have had no illusions about winning either seat, but would take a strong showing as a sign that they are making gains.

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In the other race, Democrat Gay Valimont was taking on Trump-backed Jimmy Patronis. Anything other than a crushing victory by Patronis would be interpreted as a rebuke to the Republicans.

Democrats, who have been adrift since losing the presidency to Trump and both chambers of Congress in November, are desperately looking for a resurgence – and a decent showing in Florida and a win in Wisconsin could be the spark.

Illustrating the stakes of the contest in Wisconsin, the race has set a spending record – much of that in advertising and attempts, particularly by Musk, to drive turnout.

Musk, who spent roughly $277 million on Trump's 2024 election campaign, has piled resources into the state Supreme Court vote.

Over the weekend, he presented checks of $1 million to two voters and $100 each to other voters who signed his petition.

According to the Brennan Center for Justice, more than $53.3 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 $45.1 million.

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

Billionaire Musk's Green Bay rally on the weekend 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.