A top Democratic donor has officially launched a campaign to impeach President Trump after sending letters to lawmakers and governors around the country asking them to take action against the "dangerous" president. 

Tom Steyer, a billionaire environmentalist who endorsed Hillary ClintonHillary Diane Rodham ClintonGrassley blasts Democrats over unwillingness to probe Clinton GOP lawmakers cite new allegations of political bias in FBI Top intel Dem: Trump Jr. refused to answer questions about Trump Tower discussions with father MORE in the 2016 presidential race, has created the website Need to Impeach, which asks for signatures on a petition to lawmakers. 

"He's brought us to the brink of nuclear war, obstructed justice at the FBI, and in direct violation of the Constitution, he's taken money from foreign governments and threatened to shut down news organizations that report the truth," Steyer said in the campaign video. 

"If that isn't the case for impeaching and removing a dangerous president, then what has our government become?" he added. 

The Hill obtained the letter in which Steyer urged all 50 governors and 2,000 city mayors nationwide to take public stances against Trump, slamming the president for his "systemic attacks" against the U.S. in neglecting his lawful duty to enforce ObamaCare and pulling out of the Paris climate agreement. 

"A Republican Congress once impeached a president for far less, yet today people in Congress and his own administration know that this president is a clear and present danger, who's mentally unstable and armed with nuclear weapons. And they do nothing," Steyer said in the video. 

The video comes as Democrats are preparing efforts to retake the House and Senate in the 2018 midterm elections, which Steyer suggested in the letter would be key to pursuing such charges against the president. 

A majority vote in the House is required to impeach a president. That would lead to a trial in the Senate, where a two-thirds majority is necessary for conviction.

A spokesman for the Republican National Committee criticized Steyer's effort as one that would be opposed by a majority. 

“If Democrats want to appease the far left and their liberal mega-donors by supporting a baseless radical effort that the vast majority of Americans disagree with, then have at it," RNC spokesman Michael Ahrens said in a statement.

"Republicans will continue to focus on issues voters actually care about, like growing our economy and cutting taxes for the middle class,” he said.

This story was updated at 5:05 p.m.