Donald Trump’s latest Twitter dustup is with California megadonor Tom Steyer, who is funding a push to impeach the 45th president. On Friday morning, Trump appeared to have caught wind of the effort, criticizing the progressive activist on Twitter by calling him “wacky and totally unhinged.”

In an interview with TIME on Friday afternoon, Steyer doubled down on claims that he makes in an ad that aired during Fox & Friends on Friday morning, which may have brought his campaign to Trump’s attention.

“He really is an immediate danger to the health and safety of America,” says Steyer from Los Angeles. “This administration doesn’t have a clue.”

In the ad, Steyer himself accuses Trump of bringing America to the brink of nuclear war with North Korea and undermining the First Amendment by “threatening” to “shut down” news organizations, as well as potentially violating the emoluments clause. He says the “big one” is obstruction of justice, which he believes Trump committed when he fired James Comey from his job at the FBI. Like other Trump critics, Steyer argues that the question of whether the President meets the standards for impeachment “is not a close call.”

A spokesperson for Steyer says that “well over” $10 million is being spent on airing the ad in all 50 states. When asked whether he was attempting to get Trump’s attention by airing it on a news channel the President is known to watch, Steyer says his team is simply attempting to reach Americans “of different political groupings” in order to energize a grassroots campaign to oust Trump from office.

Being the target of the President’s ire may help boost awareness of the effort — however far-fetched it may be, especially while Republicans control Congress — as well as awareness of Steyer himself, who is a mulling a run for office in California. The 60-year-old made his fortune in hedge funds, then made a name for himself as an environmental crusader after retiring from the financial world in 2012. In the last two election cycles, he poured more than $165 million of his personal fortune into supporting progressive candidates and causes, leading some to hold him up as a counterweight to the conservative Koch brothers.

With California Gov. Jerry Brown nearing the end of his fourth and final term, the race to replace him is heating up. There will also be a contest for Sen. Dianne Feinstein’s seat in 2018. Steyer says that he hasn’t ruled out jumping into either race, as he criticizes the tacks Trump has taken on healthcare, taxes and immigration.

“I’m willing to do just about anything to try and contribute to getting us back on a growth path that is just and good for America,” Steyer says. “I haven’t ruled out any of those races because I’m trying to figure out the thing that will make the biggest impact.”

Right now, he says, that’s his impeachment campaign, which could also prove helpful groundwork: Given that Democrats sometimes struggle to differentiate their positions in California, campaigning against the Trump agenda and promising to resist it will no doubt be a central part of many 2018 contests. Running or not, Steyer will be part of the mix in 2018 through NextGen America, an organization fueled by his money that works to get out the vote and support progressive candidates in California as well as other states.

When asked specifically about the language Trump used in his tweet, Steyer gave a hearty five-second laugh. “I am not going to let anything bother me or dissuade me,” he says. The ad began airing a week ago. When asked how long it will be running, a spokesperson for Steyer says, “There’s no end in sight.”

Get our Politics Newsletter. The headlines out of Washington never seem to slow. Subscribe to The D.C. Brief to make sense of what matters most. Please enter a valid email address. Sign Up Now Check the box if you do not wish to receive promotional offers via email from TIME. You can unsubscribe at any time. By signing up you are agreeing to our Terms of Use and Privacy Policy . This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply. Thank you! For your security, we've sent a confirmation email to the address you entered. Click the link to confirm your subscription and begin receiving our newsletters. If you don't get the confirmation within 10 minutes, please check your spam folder.

Write to Katy Steinmetz at katy.steinmetz@time.com.