Story highlights Steyer is planning to spend more than $10 million on an ad campaign promoting the impeachment of Donald Trump

Steyer is a prolific Democratic donor whose efforts to back Senate candidates has not resulted in many wins

Washington (CNN) Democratic mega-donor and billionaire environmentalist Tom Steyer is spending what an aide says is "well over $10 million" on a national TV ad campaign Friday calling for President Donald Trump's impeachment.

The campaign is a bid by Steyer -- who has not ruled out a run for office himself -- to "demand that elected officials take a stand" on an issue Democratic leaders have so far largely avoided.

"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 who is mentally unstable and armed with nuclear weapons," Steyer says in the ad, which largely features him speaking directly to the camera.

The ads are running on broadcast stations in New York and California and nationally on cable television. Accompanying the TV ads is what a Steyer aide said is a seven-figure digital ad buy intended to get the minute-long spot a large audience online.

Steyer is paying for the ads himself, and they are not part of his NextGen America political apparatus.

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