Hedge fund billionaire, Democratic mega-donor and environmentalist Tom Steyer holds a news conference regarding his political future and plans January 8, 2018 in Washington, DC.

Democrat Tom Steyer, a billionaire who has been pushing Congress to impeach President Donald Trump, will not run for president in the 2020 campaign.

CNBC confirmed with a Steyer representative that he wouldn't run after The New York Times first reported the development. The Times obtained prepared remarks from a speech Steyer was scheduled to give late Wednesday afternoon.

Steyer's decision came as other potential Democratic candidates considered whether to run. A flood of announcements is expected in the coming weeks.

Sen. Elizabeth Warren, D-Mass., has already announced that she formed an exploratory committee, which is a big step toward declaring a full candidacy. Other top Democrats, such as former Vice President Joe Biden, and Sen. Bernie Sanders, I-Vt., are also considering whether to run in what could be a large field. The first contests of the presidential primary season start a year from now.

Steyer, of California, was one of the top donors during the 2018 congressional midterm elections.

Steyer spent $120 million in support of Democratic causes last year and helped more than a dozen candidates make inroads into Congress.