Shortly after an ad calling for his impeachment aired on Fox & Friends, President Donald Trump on Friday took aim at the ad’s financial backer, Democratic megadonor and environmentalist Tom Steyer, branding him “wacky and unhinged.”

Wacky & totally unhinged Tom Steyer, who has been fighting me and my Make America Great Again agenda from beginning, never wins elections! — Donald J. Trump (@realDonaldTrump) October 27, 2017

The $10 million national ad campaign is part of a growing movement to remove Trump from office. Steyer, who donated more than $91 million to Democrats in the 2016 elections, has urged the party to take a tougher stance on impeachment in the upcoming midterm elections.

“A Republican Congress once impeached a president for far less,” Steyer says in the ad. “And today, people in Congress and his own administration know that this president is a clear and present danger who is mentally unstable and armed with nuclear weapons.”

Trump’s tweet on Friday is likely to bring more attention on Steyer’s campaign.