President Trump took to Twitter on Friday to deride political mega-donor Tom Steyer as “wacky & totally unhinged,” firing back at a California billionaire who is funding and starring in a television ad campaign calling for Trump’s impeachment.

“Wacky & totally unhinged Tom Steyer, who has been fighting me and my Make America Great Again agenda from beginning, never wins elections!” Trump said in his tweet.

Steyer has poured his wealth into various liberal political efforts, largely focused on combating climate change. He also spent more than $90 million supporting Democrats in the 2016 elections.

In his television ad, Steyer calls Trump mentally unstable and  “a clear and present danger” and argues that he should be impeached because he leading the country in the direction of nuclear war, has obstructed justice and has threatened to shut down news organizations he doesn’t like.

“A Republican Congress once impeached a president for far less, and today people in Congress and his own administration know that this president is a clear and present danger,” Steyer says in the ad, which directs viewers to a NeedToImpeach website.

In addition to the eight-figure TV ad campaign, Steyer has said he is also conducting a seven-figure social media buy.

In a busy Friday morning on Twitter, Trump also weighed in on tax cuts and his plans to release of thousands of pages of classified documents related to the John F. Kennedy assassination.

The president also wished good luck to Joy Villa, a singer who wore a Trump-themed dress to this year’s Grammy Awards and is now considering a congressional bid. Villa told “Fox & Friends” that she is looking at runs in Florida, California and New York.

Trump also wished a happy birthday to singer Lee Greenwood, who has performed “God Bless the USA” at numerous Trump events.