Many observers predicted that Steyer would run either for governor of California in 2018 or for the U.S. Senate seat now held by Dianne Feinstein (D), but in a Monday interview, Steyer said, "I'm not going to run for anything".
Steyer was the biggest individual political donor in the 2016 election, and his decision removes some uncertainty for California's races for governor and U.S. Senate.
The Republican National Committee dismissed Steyer's spending saying he could "light as much of his money on fire as wants", arguing that Democrats have criticized his impeachment message as a distraction.
The 60-year-old says he will not be seeking office, but he is investing $30 million into the midterms. "A youth voting bloc that will be the X factor in a wave to remaking our understanding of what it is to be an American", Mr. Steyer said.
"He's running. He's been running", Lt. Gov. Gavin Newsom (D-Calif.) told Politico in late 2016 during a conversation about Steyer's spending on voter registration efforts.
"I look forward to his continued activism in the months ahead as we campaign to take back both chambers of Congress to protect the nation from the risky Trump agenda", she said.
Tanker Collision, 32 Missing
Chinese officials dispatched several maritime police vessels, two rescue boats, and three professional cleaning ships to the area. The 32 missing crew members were all from the Iranian tanker Sanchi , carrying 136,000 tonnes of oil the time of the crash.
Most recently, Steyer has blanketed the television airwaves with his "Need to Impeach" ad campaign calling on Congress to impeach Trump.
Steyer's investment is an extension of the work his nonprofit, NextGen America, has done organizing on college campuses and online since 2014. His moves opposing the Trump administration have also spurred speculation about a possible presidential run in 2020.
The mid-term elections will be a "fierce battle for the soul of America", Steyer said.
His ultimate goal is to have Trump removed from office.
Steyer brushed off that concern, but said impeachment will not be a litmus test for which candidates he and his groups will support in 2018.
"We know this makes some of our friends and allies in this city uncomfortable", Steyer said. "We really don't have the ability to know what's going to happen after that". But, we believe this is a false choice, the fact is the two are fundamentally intertwined.