Billionaire left-wing environmental activist Tom Steyer has reportedly built what some have described as a “political death star” through his multi-million dollar campaign to have President Donald Trump impeached — laying the groundwork for a potential presidential run by Steyer himself.

“If I were a rich person and I wanted to run for president,” one top Democratic strategist told the Daily Beast, “I would be doing exactly what he’s doing.”

He could run for president as early as 2020.

Steyer has so far spent nearly $40 million on his campaign to impeach Trump and take on Republicans through NextGen Rising, his 2018 campaign to increase millennial voter turnout.

The Daily Beast noted:

What Steyer is doing is acquiring the equivalent of prime political real estate. Through his self-funded Need to Impeach campaign, he has now built an email list of more than 5.1 million members, a total that one former presidential campaign manager called “staggering” and a top digital adviser called “one of the biggest Democratic lists out there.”

The first million people reportedly signed up to be on Steyer’s mailing list in the first six days.

Republicans are reportedly also impressed.

Impeachment, however, remains Steyer’s main focus for the time being. He has even started holding town halls on the subject.

In October, Steyer spent $10 million on a TV ad calling for Trump’s impeachment. He soon followed with another.

His efforts are said to be focused on Orange County, where Hillary Clinton won the presidential vote in 2016 and where there are several vulnerable Republican incumbents.

He is also active in contests throughout the country. In 2014, Steyer’s efforts could not help Democrats hold the Senate. This year, however, he is more optimistic about his chances to help House Minority Leader Nancy Pelosi (D-CA) regain the Speaker’s gavel.

Adelle Nazarian is a politics and national security reporter for Breitbart News. Follow her on Facebook and Twitter.