California billionaire Tom Steyer on Sunday defended his campaign to encourage Congress to impeach President Trump, calling the president an “urgent threat” and accusing him of violating the constitution.

“The fact of the matter is this president has performed in a lawless way throughout the campaign and throughout his presidency and he's an urgent threat to the American people,” Steyer said on CNN’s "State of the Union." “So, to sit here and wait doing absolutely nothing is the wrong thing to do. The American people want this man impeached.”

Steyer is funding a $20 million advertising campaign calling for Trump's impeachment. Some fellow Democrats fear Steyer’s push will harm them in the midterm elections, and repel moderate Republicans and independents who may see the effort as Democratic overreach, and muddling the party’s message.

White House spokeswoman Sarah Sanders has rejected Steyer’s call for impeachment as “a complete waste of money.”

“How sad, with all the real problems in the world he can’t find a better way to spend his money,” she said. “Pretty pathetic.”

Steyer, who made his fortune as co-founder of a hedge fund, has spent more than $170 million on Democratic politics over the past three years, according to the Wall Street Journal. He focuses especially on environmental issues, such as defeating the Keystone XL pipeline, and promoting efforts to combat climate change.

Steyer on Sunday said Trump has violated the constitution by his actions related to the Justice Department’s Russia investigation, and with how he has handled his business empire as president.

“It's clear that he has violated the constitution in the sense that he's violated his trust with the American people through obstructing justice by firing the head of the FBI [James Comey] for what he said explicitly was over the Russia investigation,” Steyer said.

“He has taken money from foreign governments almost since the very first day that he took office. I don't think there's any question that he has, in fact, met that standard for impeachment.”