Washington DC - Billionaire and Trump ally Elon Musk faced an immediate legal challenge Friday to his promise to give $1 million to two voters in Wisconsin's Supreme Court race in his latest attempt to use his vast fortune to sway the results of crucial US votes.

Wisconsin Attorney General Josh Kaul wrote on Instagram that his office was "aware of the offer recently posted by Elon Musk" and said he plans to "take legal action today to seek a court order to stop this from happening."

Musk, the world's richest person and one of President Donald Trump's top advisors, has already spent millions trying to boost support for Republican Brad Schimel, who would tilt the swing state's top court to a conservative majority if elected.

The Tesla and SpaceX tycoon announced on X, which he also owns, that he would "hand over checks for a million dollars" to two people who sign a petition opposing "activist judges" – a term used by Republicans for judges who rule against some of Trump's policies.

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He has also offered $100 to anyone signing the petition.

Serious national issues are on the docket for the Wisconsin court's next term, including abortion access and rules for voting in the crucial 2026 midterm nationwide congressional elections.

Schimel is also openly backed by Trump, who wrote on his Truth Social platform this week that the race is "really big and important."

The latest stunt was a redux of Musk's earlier million-dollar prizes in battleground states during the presidential election.