Billionaire Democratic donor and environmentalist Tom Steyer will not run for any political office in 2018, instead outlining plans to sink tens of millions of dollars into an aggressive effort to flip the House majority to the Democrats.

"I'm willing to do whatever it takes to help save our country. And I believe the most important task for me, the task which I feel called to do, is organizing and mobilizing America’s voters," Steyer said during a Monday morning press conference in Washington, D.C., at an office space overlooking the Capitol.

"I'm not going to run for office in 2018, that's not where I can make the biggest difference."

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He plans to channel at least $30 million toward his advocacy group, NextGen America, in order to build out a massive army meant to boost millennial voter turnout across 10 states. Democrats will need to flip at least 24 seats in 2018 to win back the majority.

Steyer has long flirted with political bids of his own — he decided against running to replace retiring Sen. Barbara Boxer Barbara Levy BoxerThe Hill's Morning Report - Presented by Facebook - Biden, Harris launch Trump offensive in first joint appearance Bottom line Polls show big bounce to Biden ahead of Super Tuesday MORE (D-Calif.) in 2016 and his name had been rumored as a potential candidate in California’s gubernatorial race or as a primary challenger to Sen. Dianne Feinstein Dianne Emiel FeinsteinSenators offer disaster tax relief bill Democrats back away from quick reversal of Trump tax cuts Congress must save the Postal Service from collapse — our economy depends on it MORE (D-Calif) this year.

His decision to forego a bid in 2018 makes state Sen. Kevin de León Feinstein’s only serious Democratic primary challenger right now. And it keeps the crowded gubernatorial primary field in the state static for now.

The environmentalist is one of the wealthiest Democratic donors in politics — he spent more than $91 million during the 2016 campaign, including donations to candidates, super PACs and NextGen America.

And he’s blanketed the television airwaves this past year with his “Need to Impeach” ad campaign calling on Congress to impeach President Trump Donald John TrumpHR McMaster says president's policy to withdraw troops from Afghanistan is 'unwise' Cast of 'Parks and Rec' reunite for virtual town hall to address Wisconsin voters Biden says Trump should step down over coronavirus response MORE, on which he’s spent more than $20 million.

Republicans were quick to pan the effort, pointing to the less-than-unified Democratic front on his impeachment push.

“Tom Steyer can light as much of his money on fire as he wants, but doesn’t change that Democrats like Nancy Pelosi Nancy PelosiMcConnell focuses on confirming judicial nominees with COVID-19 talks stalled Overnight Defense: Top admiral says 'no condition' where US should conduct nuclear test 'at this time' | Intelligence chief says Congress will get some in-person election security briefings Pelosi must go — the House is in dire need of new leadership MORE view him as a distraction," Republican National Committee spokesman Michael Ahrens said in a statement.

"If Democrats’ message for 2018 is a baseless impeachment threat that the majority of voters disagree with, they’re going to lose.”

—Updated at 2:31 p.m.