Billionaire investor and Democratic backer Tom Steyer has launched a national campaign calling for President Donald Trump's impeachment, only nine months into the president's term.

Steyer started the "Need to Impeach" initiative on Friday with an ad calling on Americans to urge their members of Congress to vote the president out of office. In a statement, the organization said it would launch an "eight-figure" television ad purchase and a "seven-figure" digital buy.

In a video, Steyer called Trump "a clear and present danger who is mentally unstable and armed with nuclear weapons." He accuses the president of taking the U.S. "to the brink of nuclear war" and obstructing justice by firing former FBI Director James Comey, among other charges.

The former hedge-fund manager is funding the impeachment campaign, according to its website.