Minnesota Gov. Tim Walz went after Elon Musk, the world’s richest man and former President Trump’s biggest backer, with a profanity during a rally in Madison, Wis., on Tuesday afternoon.

Walz jokingly called Musk, who spent nearly $75 million on a Trump-supporting super PAC in the three months ending Sept. 30, Trump’s “running mate,” referring to his appearance during Trump’s campaign rally in Butler, Pa., this month.

“Elon’s on that stage, jumping around, skipping like a dip—,” Walz said to sustained applause.

Walz then went on to allege Musk was spending money on Trump’s campaign to buy the right to affect regulations on his own businesses, pointing out that Trump has promised to bring Musk in as an advisor if he is elected.

“That’s a hell of a buy,” Walz said, alleging that Musk’s donations to Trump could yield him billions in value.

“So in other words, Donald Trump, in front of the eyes of the American public, is promising corruption,” Walz said. “That’s what he’s promising.”

Musk said in a recent interview with Tucker Carlson that he is backing Trump to protect the country’s “core values” including secure borders, sensible spending, safe cities and free speech.

Democrats are expanding the attacks on Musk as part of a larger campaign to knock down Trump’s credentials as a populist. They have said his appeals to working-class voters are a ruse to help his wealthy friends.

Trump on Saturday used a similar profanity at a Saturday rally to attack Harris as “a s— vice president.”