Democratic 2020 U.S. presidential candidate billionaire activist Tom Steyer speaks at the Democratic 2020 U.S. presidential candidates debate in Manchester, New Hampshire, U.S., Feb 7, 2020.

Billionaire Tom Steyer, an early proponent of impeaching President Donald Trump, has dropped out of the Democratic presidential primary race.

"Honestly, I can't see a path where I can win the presidency," Steyer told supporters Saturday night, while pledging to continue working on his pet issues, including climate change and racial inequality.

He also said he would use his vast resources to support the eventual Democratic presidential nominee and other party candidates in the general election this November.

"Every Democrat is a million times better than Trump. Trump is a disaster," Steyer said. "So of course I'll be working on that."

He failed to reach the 15% viability level to win delegates in Saturday's contest in South Carolina, where he had spent more than $20 million, according to an NBC News projection. Former Vice President Joe Biden won the primary in the Palmetto State by a huge margin, while Sen. Bernie Sanders, who is considered the race's front-runner, came in second.

With more than 50% of the vote in, Steyer had scored nearly 12% of the vote in South Carolina.

He stumped and spent heavily in the early primary and caucus states of Iowa, New Hampshire and Nevada, as well, but those efforts did not help him crack the top echelon of contenders.

By the end of January, Steyer had spent $253.7 million on his campaign, according to a Federal Election Commission filing.

While he qualified for several debates, he struggled to get beyond 2% in most national polls. During the South Carolina debate earlier in the week, he had to fend off attacks from rivals, particularly Biden, about his past investments in the coal and private prison industries.

Steyer ran on what he described as the five rights; health care, an equal vote, clean air, an education and a living wage.

The former hedge fund manager was a key financier for Democrats running for congress during the 2018 congressional midterms.

Steyer, along with fellow billionaire Mike Bloomberg, combined to spend hundred of millions on Democratic candidates. That cycle, the Democrats flipped the U.S. House of Representatives, becoming the majority.

Since then, Democrats impeached Trump, which Steyer had been calling for since the 2016 election, and Bloomberg entered the race.